As to who will get the axe,
http://www.dota2wiki.com/images/3/34/Axe_firstblood_02.mp3The Fire Emblem characters probably will be replaced,
Wolf has no real chance,
I doubt Pokémon Trainer will get through unscathed,
Lucas also looks unlikely to return,
Snake is a goner,
Diddy may or may not stay, hard to tell,
Lucario probably won't make it to the next installment,
I'm unsure of the safety of Meta-Knight and DeDeDe, but it is being directed by Sakurai, so they might be safe.
As to who will stay that isn't obvious,
Toon Link will keep because of the Wind Waker remake,
and ROB will stay because Nintendo
absolutely loves ROB. For some reason. Can't say I blame them, I also love ROB a lot more than I should.
Sonic will also probably stay since SEGA has an exclusive deal with Nintendo now.