YOUR Revan still exists in your playthrough of the game. If BioWare hadn't made an RPG to begin with then YOUR Revan and any other version people had created would not have existed at all.
And if the Revan shown in SWTOR isn't to your liking, do what many do and simply disregard it as their own personal canon. For example, there are many people who don't think that anything outside of what is shown in the six currently released Star Wars movies is canon. ALL expanded universe stuff to them simply doesn't exist.
Others pick and choose what makes sense and what doesn't.
In terms of video games, this has always been one of the weaknesses with video games, but it's not so much the writing that's to blame as it is the time and money it takes to create video games. I've heard many developers say they wish they could explore every door they open up when allowing a player to choose their own path over multiple games, but it's just not possible.
Of course, if you really want to explore what happens to your particular Revan, there's an awesome way of doing it... writing fan fiction