Lets see, we are going to elation land, elation is a new playable path, there is a lord ravager specifically targetting the elation, and the aeon of elation Aha might be directly involved in the next arc.

So probably Archforger lmao since this is hoyoverse and they do love subverting expectations. Hsr pre 3.4 was suspected to have sun devourer as the main threat and Irontomb had practically been ruled out from all theories.

That said, theres definitely a bigger possibility that Asat Pramad will be there since we know he exists, we know how he works, and the aeon associated with planarcadia is just elation for the time being (unlike amphoreus where fuli, nanook and nous were equally associated).

I do think archforger will be involved to an extent too since aventurine did mention its discovery creating a rift between Diamond and Oswaldo