We just had an almost entirely Three Houses-focused Christmas banner. But since when does IS care about how soon something was, at least when it comes to Fodlan? I have a hard time seeing them passing up on Three Houses fifth anniversary. I think there's a high chance we see young Dimitri, Edelgard, Claude, etc.
But what I hope and want the banner to be is an Echoes banner. Give us the Ram villagers, darn it! Young Alm, Celica, Tobin, Gray, Kliff, and Faye. That's what I want. But, if it is Echoes, I doubt we'll get that, IS isn't smart enough to go with what the banner should be. We'll probably get Alm, Faye, and Celica on the banner, but I wouldn't at all be surprised to see Gray, Tobin, and Kliff left off for some stupid young Berkut or something.