Monroville said:

As far as Yoda is concerned, I developed the impression that he was supposed to be a lot like Pai Mei, in that he did not exile himself to Dagobah so much as he was always there. Maybe not all Jedi would go there, but those seen with great potential would be sent there for the highest level of Jedi training.

I have always thought along these lines. Even if you still have the Jedi Temple in the middle of Coruscant (which I think is out of place), Yoda wouldn't be there. He would be meditating on Dagobah, communicating telepathically to the Jedi Council. If you're willing to go to that slimy mudhole for a chance to be trained by Master Yoda, you are one dedicated Jedi! Plus, his absence in the PT would preserve the reveal in ESB.