If Ike does become Roy's replacement, I hope they adress the flaws of Roy. Specifically his stun time (get's comboed easily) and his slow speed in comparison to Marth. I really don't mind the way Roy sweetspots with his sword, but it'd be very nice if there was speed to cover the gap. I have a feeling Marth or an exact clone will at least return since Marth is so popular in competitive play.
By the way, is there a new Fire Emblem game coming out? I would suspect another character to come from there so as to promote it (as they did with Roy and FE6 in Melee).
BTW, Ike's Aether might actually be useful, because Roy's shoryuken (forgot name) was close to useless.
I believe side+b for Roy and Marth are called DED, Double-Edge Dance which goes from 1-4 hits. When you say triple slash, all I can think of is neutral aerial. Though I'm not sure if that move was three or two slashes.