Since Valiant created them, I would assume it's still theirs. Not that it probably matters though, because the characters that don't really deserve a book on their own are showing up as supporting characters ... Ninjak in X-O, Dr. Mirage in Shadowman and the Geomancer in A&A. The last thing they need to do is expand too quickly like they did before, and like CrossGen did.
Yeah, I am all for them pacing things this time as too much books at once is what ruined Valiant in the 90s. Even though I would love for Ninjak, Dr. Mirage and the Armorines to get their own series later on, they need to push the current ones first before doing so.