The tellius games are my favourites so from them, Ike is the obvious choice I would love to see both his PoR (ranger and lord) as well as his RD versions make it in. Micaiah is more popular than Elincia (going by the poll) and is a rare light magic user whilst Elincia has competition from more popular Pegasus knights (Caeda and Cordelia). I would personally love to see Soren (with wind magic as his specialty) and Ranulf because they are my favourites and could have unique play styles. Black Knight is likely to make it in some form due to being one of the series' most popular and iconic villains. I would also love to see a bird clan Laguz, the hunky Tibarn would be ideal.
I think from Marth's games we will be getting him, and Tiki (both versions) for sure. Caeda has a strong chance and I would personally love Minerva. I think Celica from FE2 has a strong chance due to her unique class and with echoes coming out in the same year. Roy from FE6 has a strong chance as well due to his popularity and iconic status for the series due to smash. I don't think we'll be getting FE 4-5 reps, at least not right away.
From FE7, my girl Lyn is basically a lock. Hector too due to him being the only axe lord and his popularity. Eliwood is less likely but still possible. Would personally love Raven, Lucius, Jaffar, Ninian or Nino but I don't think most of them have a chance. I only think Ephraim will make it in from FE8 due to him being the main lance lord, Eirika has less of a chance imo.
Chrom is already confirmed and Lucina and Robin are basically locks. Tharja is a lock too only because she's popular. Owain/Odin has a slight chance too I would say due to his popularity and Cordelia could definitely be in as well, due to being more popular than Caeda (according to the poll).
And from Fates; Xander, Corrin, Ryoma, Takumi, Azura, Camilla and Leo are basically locks due to their popularity and unique weapons. Would personally love my husband Niles to be in, as well as Odin, solely due to his outfit.