Why would I not want more Fire Emblem? I'm just wondering when the heck the new games are. I'd personally be happy with more FE.If any of this has to do with fear of a ninth FE character, I think you can relax. The best thing FE could get between now and the end of 2021 is a remake, and historically, Nintendo seems to move on from those fairly quickly. XC:DE has already died down despite being roughly a month old. Byleth should be the last of FE for Ultimate.
Of all the franchises already represented on the roster, I'd say Mario, Zelda, Pokemon, and XC are currently in the best position for a character. Paper Mario, Waluigi, and Geno are all likely for different reasons. BotW2 should release sometime by next year at the absolute latest, so it's got a decent chance of being this pass's Corrin or Byleth. Pokemon and XC are in a similar boat; both have games on the Switch that could warrant a character.