This week, Elgato updated its key application Eye TV to version 2.4. In addition to the usual bug fixes, it brings the native support for Apple TV format encoding:
http://www.elgato.com/index.php?file=support_updates_eyetv2
Handbrake allows a direct encoding for Apple TV too in its last version 0.8.5b1:
http://handbrake.m0k.org/
It would be interesting to know the first numbers concerning Apple TV sales, but is Apple did not communicate about it is most probably because they are lower than expected, at least in Europe.