Even if we're getting a demo at E3 it doesn't necessarily mean the game is finished. Like with everything they show before release date, things are subject to change, and there's still a pretty long wait till Summer. There's still hope.We might not have Chrom at E3, assuming his voice actor is not ready yet:
http://www.reddit.com/r/fireemblem/comments/27kv15/asked_matt_mercer_the_voice_actor_of_chrom_if_he/
As for the 3DS version, I can see them maybe re-using voice clips from Awakening there as it would be easier and kinda make more sense. But hey maybe this means we get a unique, different character to rep Fire Emblem?