Eh, I'd argue Estelle is in a bit of weird position in terms of Falcom reps. At least in Japan, all of the mainline Trails games are on or coming out for the switch, except for Trails in the Sky trilogy (Estelle's games).
However, the president of Falcom did say in an interview that he wants to remake the Trails in the Sky trilogy (link to the interview here
https://www.usgamer.net/articles/fa...ike-to-recreate-trails-of-the-sky-games-in-3d), which can really improve Estelle's chances for being the Falcom rep if these remakes do happen. But there hasn't been really any news for the Trails in the Sky remakes so if it does happen, it might happen after the Smash DLC is over.
I believe Estelle is major recurring character in the Trails games and especially in the Trails of Cold Steel games (I actually haven't play those games yet oof) as well as being the first protagonist for Trails. So you can probably argue that Estelle would be a better fit than Rean to represent Trails. Maybe?
Generally, I think Estelle has the same chance as Rean, but I think Adol slightly has the advantage over them due to Ys having more of a legacy. (I can probably write more about but my Falcom knowledge isn't the best and I don't want to spread misinformation).