not sure about this. but wouldn't they generally be just as likely yet to be dealt as in the opponent's hands (relative to the the respective total number of cards).

i.e. if you say, but there's expected to be a few spades in my opponents hands (folded or live), then you have to subtract the 16 cards from your card count and it should get you back to the same sort of percentages.

obviously if you have two spades and flop comes two spades and lots of people stay around or are aggressive, then yes, maybe there are quite a few spades in opponent's hands.

i asked a similar question. namely if 7-8 see the flop and you have AK, can you really assume the ace has three cards to pair with i.e. i'd assume maybe 1 or 2 aces are out. although i guess you could assume there's another ace out when a couple of early callers come in.

all the more reason not to play A7o, not only kicker problems, but maybe with 6-7 callers, there is only one ace left in the deck.

vis-a-vis your question, before the flop your opponents are just as likely to be playing suited connectors of other suits.