I'd like to see it support "templates" for various sub-types of RPG's--strategy, action, etc. Similar to how Ingie Game maker has different genres you can use. Ideally, this would be done by improving RGSS even further--to where there are "official" scripts for each type that you can simply swap out and modify--but having a setup like Indie Game Maker where each "type" is a separate subset wouldn't be so bad either.
Additionally, I think they may eventually see fit do away with the grid-restriction and move toward pixel-based movement and collision detection. Probably not in the next version, but I'm sure it'll come up eventually. Or at least they could make it so that the collision detection aspects can be modified reliably without glitching all over the place (the problem with current 8-direction, pixel-movement scripts.)
As for 3D, I wouldn't touch it with a 10-foot pole. I barely have enough time for managing a project in 2D, so 3d would be well beyond my scope.
Still, I think there is a niche for serious one-person-/small-team developers who want to make 3D RPGs, and are willing to put in the Time, Effort, Programming and Math that such a project requires, with a bit of simplification to keep the logistical overhead down. Basically, a way to make such a project manageable for one or two programmers, perhaps at the cost of flexibility and graphical capability. And of course, default assets and an editor that could modify them. It could be marketed toward those with a bit more tech/programming/math savvy than RPGMaker requires, and work as a happy medium between RPGMaker and a typical 3D engine.
It would be too much for most of the people here (myself included) but could fulfill a niche in the market. But if there's something like that out there already (no the PS2 versions don't count,) feel free to kick me. I have calluses.