Forget anything Embraer. The A220, according to JetBlue is a whopping 30% cheaper to operate over The Ejet. Even more so if your in bed with Airbus and negotiate sizeable orders.
If anything I would expect 10-20 odd A320s converted into 20+ A220s.
Q400 are still in production so a reorder will probably occur as it’s still an absolute weapon vs anything on a Jet cost wise.