Tbh

I personally don't think that they'll pull another curve and give us masked marth again, since she's already in the grail system included.

New units would be cool though. The only question is which ones...

new camilla. its time boiss

The first sounds like it matches the story theme. So it might be a character linked to the story (maybe someone we don't know?)

The second one has very likely a princess as TT unit. One option is Veronica, but it might also be an (seasonal) alt for a princess we already have.

Of course 'life is just fleeting' could also be linked to Azama

The thing that interests me the most about tempest trial are the Seals, free character is apretiated but i'm not that interested in them, mainly because they never released a character that is unique in doing something that the character i have already built up can't do, everything they do can be done by a character in the normal summoning pool, Smolzura can be an exeption but at the end of the day she is just a dancer.
While with seals i can be used in many builds, like Atk/def bond which is the best bond possible making some builds work so much better

I would love more free M!Marths so I don't have to spend grails on her. (I'll still need to buy one copy since I missed one in the first TT, but still.)