The question about first party interests me, for a very personal reason (no need to invoke the Nintendo authority, it's just for sharing).
Not counting the Miis, there is a total of 23 first party licenses represented by at least 1 Fighter.
Not counting the 4 upcoming DLCs, there is a total of 9 third party licenses represented by at least 1 Fighter.
With 4 new licenses in the DLCs, the total would be 32 different series.
With 1 new first party license and only 3 third party licenses in the DLCs, the ratio would be 24/12 (or 2 for 1).
I would like the overall representation to be that way. I like the total number of 32, because it is a
power of two, like all the powers of the concoles (8-bit, 16-bit, 64-bit...). And I like the idea that the Nintendo series can be exactly twice as important as the other series. So I'd like a new Fighter from a new Nintendo license.
However, my belief is that the pillars theory works, deconfirming all series already represented by Assist Trophies (including
Monster Hunter) or Spirits (including
Custom Robo,
Drill Dozer,
Excitebikes,
Jam with the Band,
Nintendo Wars,
Sin and Punishment...).
Finally, I have no idea who could be a possible new Fighter from a new Nintendo license, even if I hope for one.