I'm getting rather tired of fighting dragons, liches, mindflayers, humans, elves, drow, dwarves, abishai, glabrezu, balors and cornugons. In other words, common Faerunian entities (considering that the BG series somehow finds millions of ways to gate the denizens of the Lower Planes to the Prime Material Plane).
Personally I don't see why another CRPG based on the planes can't be produced. After all the relative unpopularity of PST stemmed from its lack of advertisement and a small demographic (i.e. pariah players who actually dare to blaspheme that intelligence and computer games are not mutually exclusive
), and not on the unique setting per se. There's no requirement for the new game to be based so much upon text or philosophical discussions; I would be perfectly happy with unique settings, and interesting situations, characters and items, plus a decent plot. Making a game about the inner planes would be fine by me.
Such an endeavour's probably quite difficult, but that's the challenge, isn't it? After all the BG series and its IE counterparts have a reputation for quality design and extensive effort. I would be exceedingly irritated and disappointed to see the next BG or BGs become commercial udders for the corporate milkman.