If you think Blitz3D will only work for a few more years, why use it?
Because the same is true of everything else too. If you can't accept it, you shouldn't be making games.
You could make a game with anything, and if it's that good it'll be around forever, no question.
I'm getting the sense that you never wanted straight answers to your question, but you just wanted people to tell you what you wanted to hear. If you'd said that in the first instance, I could have obliged.