There's no new 50-seaters available and 700's with 50 seats are not economical in most situations, my guess is even if they end up storage for a while the ERJs will end up back in service eventually.

I follow the mfg side of the industry closely, there are no rumblings about new 50 seat designs. Maybe turboprops, but even that's a hard business case since the US airlines have a clear preference for jets... very hard to succeed with a clean-sheet regional aircraft if you can't sell it in the US (ask the people who built RJ's that didn't comply with our scope). Economics/carbon politics might get the US industry over it's prop disdain. Maybe.