Obvuiusly whilst flying your Tie Advanced in the middle of a huge combat arena is the
best time to start wondering about the genaelogy of the guy you are shooting at

Of course, the Jedi like ability to figure out that sending Luke to his own uncle, and not even changing his name was an awesome way of keeping his hidden

As far as the trailer is concerned,
I think the lightning that hits Yoda is not Sideous, I think it's Dooku. I have a suspicion that Yoda will fake his wn death. The duel is most likely ol' Dooks as well, that would be more in running with the 'tradition'.
Edit : What I would have like to have seen was Yoda defeating Dooku on Dagobah, thus explaining the cave that Luke had to enter, but that, apparently, will not happen
