Nintendo started the trend of farming out their IPs to external developers for crossovers.
First it was Koei's Nobunaga Ambition x Pokemon, now it's Atlus' SMT x Fire Emblem.
And Iwata said there will be more.
Going with the trend that all the properties so far were SRPGs, it's probably gonna be that horrible Call Of Duty x Advance Wars proposal... Nah, all developers so far were japanese, that has to be either Capcom or Square Enix.