AT&T assured the courts that DIRECTV would be around for at least three years after their proposed merger. Since it seems rather likely that the deal won't get done until 2015 or later, I'd guess there's not much anyone can do outside of DIRECTV changing their name (something that could be disastrous should the merger fall through).
If the merger with AT&T is completed, I'd wager that the DIRECTV name (and the company with which it is associated) will indeed morph into something not entirely recognizable more or less on the 36 month schedule. After all, who remembers what companies went into the old or the new AT&T (or even that there was an old and new AT&T)?