I think MU as a Tactician, for the time being, is DEAD. We've never needed the tactician, that is, someone who functions as a stratgist, to be an Avatar/My Unit character. I'd argue the role was better suited for someone more rigid, like Soren. With that in mind, I think Robin for the time being is benched.
Kamui, who seems to be the MU/Avatar for FE14, does not seem to be a tactician. S/he seems to be the lord outright. I think, with the success of the MU model, they will keep trying different things with the character until they find what works best. If this lord thing doesn't work out, they might revert to a tactician MU or something else in a future instalment.
As for Robin, as a character, I don't think we've seen the last. Given how much MONEY was printed by FE13's DLC and merchandise, we'll see plenty of our hero in one form of another, be it SpotPass or paid DLC for FE14 and other products. We are likely to see future references, if not new appearances entirely. Appearing in Smash Bros is just so much great publicity for a character and the franchise they're from. Look at how well they marketed that "Marth" would be in Awakening.
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