I think folks are underestimating how much of a damage bump martial classes, in particular, got. So I think DMs will have to adapt to that after watching their players demolish what would previously have been a challenging encounter. Hopefully the new CR rules will help, though we have seen little of them so far, so it’s tough to say.
Old adventures will work, but will need balancing, though as others have pointed out, you always have to adjust for each party, anyway.
Monks will be the new hotness.