Daniel Erickson of Bioware gave an interview to russion gaming site goha.ru where he said:
M: So this is, incidentally, means that you will support the fashion for the interface that will make the players?
D. E.: Well, yes, this, in general, has become a standard, support for mods, so that everyone can make yourself comfortable client."
So, yes I think The Old Republic will have support for UI Addons.
