Short answer: Soon. SOON. <insert soon owl here>
Long answer: As Thalia admittedly wasn't as many accounts/characters as other servers of course it was first and going to be quick. As for the backend there was some gitches and unexpected problems that happened, albeit minor, see
Thalia merge - Issues FAQ
As for the additional server merges, I'm sure more testing needs to take place as well as getting through some backlogs on our backends before additional work can be done. It's still on the list of course and hasn't been forgotten, we just don't have any additional information as the scheduled workloads have to be balanced by the Product director himself regarding the sysadmins and the other projects they have going on. In short, see Short answer. It's coming, we'll announce it as soon as we can, sit tight and bear with us, as I don't think many realize the amount of work and preparation involved. It's not just flipping a switch and it's done. It's definitely more than that, folks.