From the description:
"Just as in the first Choose your Legends event, the top characters will appear in Fire Emblem Heroes as Special Heroes sometime in the future!"
Like I would not be surprised if we get Hector, Chrom, Tharja and Camilla as Brave Heroes before they do the next Brave Heroes, but I'm looking at this and this looks like another Voting Event is going to happen. Well, since it happens on the 21st, we'll see soon enough.
That being said, I wouldn't be surprised that if we got Seasonal Heroes for February, it wouldn't be Valentines/White Day Heroes, but "Anniversary" Heroes. I mean, being the 1st Year Anniversary of a release is sometimes enough to warrant a special set of Heroes. Not sure about some other Gachas, but Fate/Grand Order did release Da Vinci for the 1st Anniversary and Sherlock Holmes for the 2nd Anniversary.
Other potential scenario, we get Leif and other Thracia 776 Heroes, so the whole gang will be around in time for Anniversary.
Sword Hector, I'd be fine with. Camilla with Bolverk would be cool. Chrom should get Staff, especially now that Staves have gotten much better. And for Chrom + Pain/Savage Blow memes. Tharja with a Bow......I wouldn't mind it if it happens.....but I would like to see Dark Knight Tharja.