Things like NWN or BGE are extremely unlikely. There is very litte precedent of commercial game companies going back and porting their old releases on mobile phones (if you have examples of that happening, do tell). With someone like LGP, odds are slightly better but most likely ports are going to be things that are open source and not 3d accelerated. The open source part is extremely important and porting to the n900's variety of opengl is apparently not trivial.