Very interesting answers.
I hope for a 2D strategy game revival.

Seconded. I was desperate for the expansion pack.

Refreshingly frank and honest answers. It's a shame that things turned out the way they did for Original War. But at least the developers are still working in the industry. Something which is so often not the case with developers behind commercial failures.
As for 2D, I don't think it's advantageous for RTS at all these days especially given the inherent gameplay advantages of 3D. Original War worked very well as its focus was on smaller groups. Even so, 3D could potentially be of benefit.

I concur.
While I do agree 3D is way to go especially in RTS and other fast paced games it does not always bring added benefit, at least to end user. This seem especially true in paradox games when they switched from their old 2D engine to their new 3D engine. From user standpoint the new engine is needlesly heavy and cumbersome nor does it bring any features that could not be performed by simply modifying the old engine. In general grand strategy games benefit little from using 3D instead of 2D.
I also think that use of 2D graphics for OW was right choise at the time for many reasons including hardware available at the time, availability of 2D artists and similiar lack of people with exprience in 3D engines and 3D art and modelling. Obviously today the situation is completely reversed, however this is not to say that 2D game could not reach commercial success especially in indie game market (the future of PC game industry).

Yes, it was the right decision at the time. The tansition to 3D was made at a time when 3D generally looked a lot worse and caused a reduction in environment size and interactivity. Bad news all round in other words.
But that was a decade ago. Now even the most 2D games by nature can be improved by 3D. Take Trine as an example. Plus, if you look at Deathspank, it's all too clear how 2D charm can be retained in 3D titles.
Now there's no doubt that more could be made of a 3D sequel to Original War than a 2D one. Although, as they've stated, that's not very likely at all.

Well, as far interactivity is concerned Ultima 7 is still unmatched and unfortunately enviromental interactivity has generally made nosedive since transition to 3D. Today's developers tend to compete almost solely with graphical quality and ignore features and enviromental interaction that can not be easily shown in screenshots or promo videos.
Piranha Bytes tried to add some interactivity in Gothic but they are exception, not a rule.
But this is not always the case. Lets take Civilization IV as another example. Both number of opponents and world size were greatly reduced due to new 3D engine being such a resourcehog that computers available at the time were barely able to handle the map size and available opponents without choking or forcing player to wait hour between turns. If they'd used 2D engine there could have been more opponents and maps could have been larger and they still could have implemented all the new features in Civ4.

But even Civ4 was four years ago now. It was scaled down because the engine wasn't optimised enough (Total War series proves that more could have been done) and because it looked to me like they valued prettiness over quantity.
That doesn't change the fact that more could be done now, just so long as you've got the right developers behind it.

But that also does not change the fact that they could have done better game continuing to use 2D engine nor is there any guarantee that next Civ or one after that will be better than if they'd continued to make Civ's with 2D engine. The point I'm trying to make is that 3D by and in it self does not provide any benefit if your game does not have any features that could be made only in a 3D engine. Stick figures will remain stick figures no matter if they are made with 2D or 3D. Military unit symbols remain just that if you make them with 3D or 2D. etc.
Same goes with many other things like voice acting. Voice acting can improve a game sure but bad voice acting can ruin it. Also due to cost and time the voice recoding takes ammound and variety of dialog have to be reduced so unless you can hire good enough voice actors and number needed you're probably better off with completely or mostly writen dialog. Voice acting by and itself does not improve the game.
Same with CGI animation over drawn/2D/engine run cutscenes. Sure CGI cutscenes are wonderfull and all but making good ones cost both time and money so what's the point if making all those wonderous CGI cutscenes means cutting back in everything else? You may well end up with completely shit game that has great cutscenes. Why not make CGI movie instead if you care so little about the game it self?
And the graphics whoring these days. It sometimes feels that some teams have 100 artists/modellers for every animator/programmer/AI scripter/writer/worldbuilder etc.. Yeah, sure that way game gets beautiful graphics but game is buggy as hell, engine broken and unoptimised, stick figures have better animation, 6 year old could write better dialog and story on his/her spare time, AI gets lost every few meters and can't find it's way around single rock and world is stale and static as hell.
I probably could go on ranting all day about current state of game development but hopefully I've made my point. In short, no technology or feature should be used if it does not provide clear benefits (no, just being pretty or cool does not cut it even if marketing loves them) and no single area of game development should be overemphasised over others especially if it means other area(s) is negleted.

What a discussion! I feel compelled to add my point, since I made the question in case :D
To put it simply: I don't think 3D adds anything to RTS gameplay. Command & Conquer 3 uses exactly same mechanisms as StarCraft. The only real change is fancy zooming in and out. Also, 2D graphics looks less artificial, since it lacks visible polygons and overlapping textures.
In terms of RPG gameplay, also present in Original War, I found 2D backgrounds looking really more "artsy". Sure 3D detailed maps are all good and nice, but some old Infinity engine backgrounds (from Torment or BG2) are true masterpieces. 3D games lack many little details, because they're usually made from combining few pre-made objects, and adding only one little object to display it one time for the whole game just isn't worth the effort.
As for the Original War itself, it's detailed backgrounds and pastel colours were really appealing to me and I can't think of any way to present them in 3D

Ultimately, what it boils down to is: Could a 3D RTS game be superior to a 2D RTS game today?
I think that, certain developers' own abilities aside, the answer is a clear "yes". Everything from the more flexible camera to the more varied terrain to the role physics can play in the game all add up to a vastly superior experience.
You say that more units could have been possible with 2D, yet Total Annihilation, the game that pioneered the 3D RTS allowed for hundreds of units per faction. That was 11 years ago. If developers can't manage that today then they should find another profession.