From a technical standpoint: No.
I'm on probably my dozenth account now. The majority of my jumps are because the instance I'd chosen became unstable, had long and/or frequent outages, or just died and went away completely with no warning.
Even the biggest instance I've ever joined, lemmy.world, choked whenever there's a large exodus from Reddit or a lemmy upgrade or a bug farts in Belgrade.
The instances with fairly open enrollment will likely break under the load. The smaller instances with ridiculous sign-up requirements and/or a need for manual approval of accounts will discourage people from using Lemmy at all.
And because of those technical issues...
New instances will pop-up quickly from determined Redditors, because the stuff that's already around can't keep up. Then those new instances will become the heavy hitters. The ones we have now will be vulnerable to atrophy and becoming insular. The overall Fediverse will be vulnerable to the silo effect, diluting its value to folks, as it will basically be RedFed versus OldFed.
From an end-user standpoint: Also no.
The "culture" would shift practically overnight. I've already seen that happen. When I first got here, people were actually kind to each other. Users stood up for others and disparaged others for being hostile, aggressive, overly negative, etc. Then we had the API-calypse surge. Now those radically kind days are long gone. It happened fast. I tried to keep it up in my own small little corner, but even I don't do as good a job as I should.
While the Fediverse may be "strong" overall, the individual pieces are too fragile to handle a significant Rexit onslaught. If even a small fraction of all Reddit users came to the Fediverse en-masse, this place as we know it would be gone.