Mind you, I believe the CRISIS will result in all of the worlds combining to make what amounts to the typical DCU.
Aliens, metas, and more.
I really hope not. The multiverse is an asset to the Arrowverse continuity, particularly in terms of the very different worldbuilding and history of Earth-38 as opposed to Earth-1. It would be a huge mistake creatively to eliminate that diversity. Indeed, DC recognized long ago that they'd made a mistake by wiping out the multiverse in
Crisis, and they've long since restored it. So it doesn't make sense to assume that the Arrowverse would repeat the same mistake.
I mean, look how casual it's become for them to use Cisco's little extrapolator buttons to hop between universes for crossovers, or to phone up other Earths to talk to Wells doppelgangers. Interaction between universes has become so easy that there's no storytelling need for collapsing them into one. And multiversal antics are such a routine part of
The Flash's storytelling now that it would be a major loss to the show. And
The Flash is the highest-rated Arrowverse show, if I'm not mistaken. Thus, I really doubt that the producers have any desire to eliminate the multiverse.
I think it's more likely that their version of
Crisis on Infinite Earths will be about the heroes successfully
preventing the collapse of the multiverse -- probably with some worlds being lost, but many, especially the core two, surviving. After all,
Elseworlds already laid the groundwork for the idea that the "destiny" of the comics characters can be changed, when Oliver convinced the Monitor to prevent the deaths of Barry and Kara (both of whom died in the comics' Crisis). Similarly,
The Flash established that Cicada wasn't the same guy in their reality that he was in the comics, because Nora's time travel had altered history. So it stands to reason that they'll follow that precedent with CoIE as well -- that it will specifically be about making sure that things
don't happen the same way they happened in the comics.