[wyrd]

Plenty of fish play any two suited cards, so I wouldn't be so quick to dismiss a possible 4.

I'd fold. The way it's played he probably hit a set of 5s, giving him a boat. If he had a worse Q why would he suddenly go all-in? Makes no sense. If he had a 4 I could probably see him doing this because of the two diamonds. AA or KK I'd expect some sort of bet or raise on the flop.

So given the choices and the betting, I'd put him on a full house, 5s and 4s.