I'm not sure if theres really any qualifyable proof for either side of the argument but. I think standalone RPGs (including the popular franchises) tend to cater to a more/less unique play experience, which I think tends to make it on the niche side of things. Moreso for JRPGs rather than WRPGs.
I think the concept of hybrids though are pretty much the way of the future and MMORPGs are anything but niche, so I guess it's where you draw the line.
RPG element/style gameplay mayu very well be implemented in virtually all games on some kind of level in the years to come. However, I think the classic 1 player hero story / D&D RPG is going to be something of an underground following (or Dungeon following if you will).
"Let justice be done though the heavens fall." - Jim Garrison
"Ask not your horse, if ye should ride into battle" - myself
