Y'all are acting like this is not a thing : http://store.steampowered.com/sub/4838/

Does it contain Mega Drive games that are not by Sega themselves? No.

Yes there are some commercial ventures out there, cinemaware , dotemu. But not that many, and generally quite old stuff.

As a bridge? No. Maybe as a holodeck.

Damn. Shut down like it was nobody's business. :P

The short answer is "probably not" in the general sense. There are two real ways that this could happen. The first is that the rights owners of the individual game properties port the game to the PC themselves or by using emulator technologies and then bring it to market themselves, which is what SEGA and some other companies have done. Some of their titles are available on Steam now for example. Keep in mind that isn't something that Valve or Steam did, they're just the store - the company that owns the games decided to bring these games back to market using emulation technologies and they simply chose Steam as their retailer. An alternate similar option would be if another company licensed or acquired the rights to a console game to port it or use emulation on PC and did the work. In either case, they could theoretically choose to use GOG as their retailer as well if they wanted to, but that's up to them. On the GOG side of things, GOG could accept or reject such titles in the GOG store based on their usual criteria as to whether they think a given game is a good fit to their customer base. I'm sure some titles would be welcome while others might not depending on many factors.

The second way this could happen, would be for GOG.com themselves to purchase or license the rights to a given game and then either use emulation or porting themselves or hire a 3rd party to do the work. While this is certainly theoretically possible as GOG is now a game publisher as well, and they have acquired the rights for some older games such as some of the old SSI D&D games for example, they are going to be highly selective as to which titles out there they contemplate purchasing the rights to and how much effort and thus expense/investment is required to bring an old title (of any kind, DOS, console, Amiga, whatever) into working shape and bring it to market. Obviously they'd have finite resources to do this, and they'd likely want to invest in the products that are likely to have the biggest beneficial return on investment and potential demand with the least amount of overhead and risk involved. Additionally if they wanted to do this for a given game of any kind, they'd have to be able to actually acquire the rights to it to do so, and the owner(s) of the rights to a given video game or game franchise may or may not be open or interested in doing this sort of thing at all. Then there is also the case where it is sometimes difficult to impossible to even track down all of the rights owners to some titles or get them to respond.

So while there is nothing stopping such a thing from happening, it seems extremely unlikely that we'd see something like this happen on any large scale or any time soon. It is really something that is in the ball court of the owners of the given game properties to decide to do. When GOG's publishing wing goes looking for future titles to try to bring back to life via obtaining rights themselves though, they're most likely going to be looking at former PC titles, things that will run with DOSBox/ScummVM or similar that take low effort and minimal investment to bring to the store, and only such titles where they believe there is a high enough demand in the user base to make a worthwhile ROI.

I'm not sure GOG would be best company to initiate something like this though, it would be branching out and spreading themselves thin rather than focusing on doing more of what they do best. Either way though, they are unlikely to publicly speculate about it I imagine, so one can always wish for anything and who knows what the future may hold.