The flip side is that identifying all users running TextSecure will get a lot easier, I presume. Previously telcos saw encrypted SMS (sometimes) and connections to GCM. Now they will see connections to TextSecure.
There are possible ways to mask that, though they'd likely still draw attention.
Assuming that any given endpoint was already a surveillance target, the advantage here is that the traffic cannot be used (or is less readily used) to determine contacts -- who's talking to whom.
Assuming that any given endpoint was already a surveillance target, the advantage here is that the traffic cannot be used (or is less readily used) to determine contacts -- who's talking to whom.