Well, Minoru Nakai, like basically everyone on Capcom's staff, says that they'd love to do it but the opportunity hasn't come up.
Nakai (hey, double the k and you get the name of MoTB ruins, I just noticed that) said that it's a matter of resources. DASH is risky, and Capcom apparantly doesn't want to draw resources away from the "sure" money makers. This is probably why Trigger makes as many cameos as he does; what's needed is something that'll get Legends a lot of attention.
I still say Trigger should have made an appearance in Smash, if Inafune would have picked up the damn phone. If they got Fire Emblem outside of Japan that way, they could work wonders for Legends.
Seeings how that ship has sailed, maybe we can beg for the unlikely event of 5 Island Adventure being ported to WiiWare.
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