Personally, while I'd love to see FE6 get remade, I could live without it. It was in the "Last" hand held generation before the current one- It's too new (Even if it was released early on and never outside Japan). Now, if they do release it, they should do a prequel/sequel deal like FE1/3 had- In other words, one should lead into the other, and both be on the same cart preferably.
But, that's my fan-dream, so, that aside.
Personally, I would like to see FE4/5 remade. I never got to play them (And the emulator feels just off enough to me to warrant me not playing it anymore; Damn me for getting into games during the N64 era), and I'd like to see what they do to upgrade it.