Shonen Jump has the news and says Yuna has the ability to control two Aeons at the same time. The magazine has a screenshot that shows Yuna controlling Shiva and Ixion for simultaneous attacks. Yuna can also summon King Bahamut in Dissidia 012[duodecim].
Her EX Burst sounds absurdly powerful. Translated as Sending off to the spirit world, this attack makes Yuna call all of her Aeons for a consecutive set of attacks. Hmm.. I wonder if that includes "secret" Aeons like the Magus Sisters, Anima, and Yojimbo.