With today's new Living World release, Arenanet has announced their announcement for the next expansion (funny how that goes, isn't it?)!
It appears that, after the finale, we won't have to wait long as the announcement will be next week on Tuesday, August 1. You can tune in at 9:00 AM Pacific Time to watch it live! That is 18:00 CET or 17:00 UK time (which makes a lot more sense now, doesn't it?).