I just realized that would be another surprise ruined in the OT. We now know who and what Yoda is (what he looks like). When we first watch TESB we don't know who the crazy little green guy is. Again, I don't like tampering with the OT, but if we changed Obi-Wan's lines in TESB from "Luke, you must go to Dagobah. There you will learn from Yoda, the Jedi master who taught me." to "Luke, you must go to Dagobah. There you will learn from the Jedi master who taught me." Luke also whimpers out Yoda's name and that too would have to be edited out.
But, as soon as we see Yoda the gig would be up. At least there would be a surprise in who the Jedi master is.
If we make it so we think that Yoda is dead at the end of ROTS that would a pretty cool intro for Yoda. He's alive!
You have any ideas on how the supposed death of Yoda would play out MeBe?