It's pretty obvious "what happened." Here, I'll show you:
Yeah. It's as simple as that. Due to limited suppliers / demand, Japan will come out with only so many RPG's in a given period of time. Many of them have been going to handhelds.
Well, another major reason is how JRPG's on consoles (especially HD) require much higher development costs / time than they ever did before. This is because in theory people believe stuff like 2D is only acceptable on the DS, and they will only accept great 3D graphics for their games.