...Or did I only read that he'd never replace the puppet Yoda with CG in the original movies? Maye I misquoted. Very likely.

I wouldn't be surprised if George would change Yoda in ESB to a CGI version for the 3-D version. He said himself CGI thinks look better in 3-D. But the 2-D version Yoda is pretty safe, I suppose.

I remember in an AotC documentary, when they were making CGI Yoda, they tested him on, well, ESB footage, so it really isn't much of a stretch that ESB CGI Yoda can appear. Either as a main or bonus feature, that remains to be seen.