Does it really makes any sense becoming a source and hid it away from people, what could be their reason for not letting people know they have become source. Don't you think they had something in mind for not updating people over here?
Well, just as you said nothing is hidden under sun, same it's applicable to the forum with time the list must sure comes out then we see the newly approved merits sources.
The merit sources list is not published just like we have the DT list publicly available. One of the reason maybe that they do not want everyone to know who are merit sources as then people will start PM them asking or begging for merits. Other than that, I don't see any reason not to make that list public.
Come to think of it, was there any need for the new merit sources to come open and make announcement of their merit source approval by Theymos? IMO they should have just swallowed the announcement instead of making it public because some merit beggars might still intrude in their PMs and start begging for merits. However, hiding the identity of the merit sources cannot stop merit beggars, it can only reduce them, after all some merit sources have already revealed themselves. If any user beg for merits from any merit sources in their PMs, they should be tagged as merit beggars so that others can avoid and even add such user in their ignore list.