I'm currently using 15.04 and having some sound issues but next month the next Long Term Support version is released with Wily Werewolf. Will GOG continue to stick with officially supporting 14.04 or will they move to the next LTS to keep things current?

I preferred it when they used real animal names.

But there is, it's just people don't really know what they want. They could easily adapt any distro to their liking, instead they distro hop out of no obvious reasons.

They should make.. distro addons like Firefox XD
Same base core but optional customization parts. :P

GOG says in the Linux FAQ that they will always support the latest LTS release, but 16.04 will be the next long term version, not 15.10!

Who should make that?
Aren't Debian, Ubuntu, Linux Mint etc. exactly what you describe? You can make your own Linux Mint by installing everything that sets it apart from Ubuntu manually. - There is little reason to use standard Ubuntu in the first place, though. :) ^ This

Uh.. some Linux dev? I don't know lol, I'm just a Window user.
But can you really easily add\remove\disable parts of the SO like addons? :O
I thought that Debian->Ubuntu->Mint they were completely different project based on the previous ones.. no?

Just a small correction. The next Ubuntu version -> Willy Werewolf is a short term version number 15.10. The next long term version is 16.04 LTS coming april 2016.

Yes, you can do that by using a Package Manager, Terminal or often a Software Center.

I don't know what you mean by completely different projects. Every program that runs on Ubuntu should run on Mint, though sometimes you may need to install a library first. AFAIK, the Linux devs base each new Mint version upon a current Ubuntu version.
Debian is more different from Ubuntu and Mint, so, getting Ubuntu to work exactly like Debian will require more work.

Not sure if joking/trolling, but I'm gonna answer nonetheless: because there just isn't something everyone wants. People are different and they want different things. So it's just great that there exists diversity so everybody can find the OS/distro that best suits their needs/desires. Definitely much better than having one company controlling where an OS is going (hello, recurrent complaints every time a new Windows version is released).

But anyway, your question was completely off-topic. The OP isn't asking GOG to support more distros, but supporting the newest LTS of an already supported distro (Ubuntu).

It's actually the other way around, by default Mint has a lot more libraries than Ubuntu. The only reason I can see why one would want to use standard Ubuntu is for the Unity desktop environment.

Nearly every store that supports Linux really only supports Ubuntu (Mint is Ubuntu in all but name). That said, I have had minimal issues running GOG linux games on just about every distro I have tried.