Tigole has been pumping out few revelations of future content, from the outcome of the “Missing Diplomat” quest series, down to how many players Tower of Medivh will possibly accomodate.  Indirectly, he does mention there is a programmed Burning Crusade Beta in the way:

Tower of Medivh
Actually, my point was, that we are looking towards doing many 5 man dungeons in the Burning Crusade. As for Karazhan, our current thought is that it would be a 10 person raid. You mention that you hang out with 8 people—I think Karazhan would be well within your reach.  In any event, things will change over time, as we play the Burning Crusade in beta and get a feel for what players want and need.

We’re not going to do anything to deliberately alienate anyone from the game. We try very hard to keep players happy—from casual to hardcore”

Missing Diplomat—King of Stormwind
” This quest line is going to be re-addressed in the future. In patch 1.9, the King has mysteriously escaped from Alcaz”