Your chances of a Blitz3D game running in two or three years aren't great. DirectX has traditionally struggled to maintain compatibility beyond three versions, and DX7 is already three versions behind. The chances of everything working in ten or twenty years time? As close to nil as it's possible to get.
On the plus side (I guess) almost no one will want to play a game which is based on twenty year old technology anyway. Particularly 3D, which dates far, far quicker than 2D does.
On the plus side (I guess) almost no one will want to play a game which is based on twenty year old technology anyway. Particularly 3D, which dates far, far quicker than 2D does.