There will be a few that's for sure, it's human nature and some are born gamblers. I remember sitting in a pub directly after we beat wigan in the quarters listening to four lads on the next table. Their plan was to listen to draw on the wednesday and if we got catalans one lad booked the train tickets and another one booked the match tickets, if it was saints or wire everything was on hold. I also remember a customer of mine booking a FLIGHT and hotel for the cup final when we were up against huddersfield in the semi of 2006. We'd murdered em away from home the same month and they were struggling. Guess what, he ended up flying down to watch huddersfield in the cup final that year not leeds. There will be a few from warrington taking a gamble believe me.
Hmm, think you may be under-estimating the tightness tbh!
Most people know that they won't be able to get rid of tickets as there are always plenty knocking around, and if you can't transfer or cancel your train/flights then you are pretty much giving money away. There is no real reason to gamble tbh as it is easy to get tickets. Hotels are well worth booking in advance and then cancelling if you don't make it as there is no cost (my parents have done that as watching neutral teams doesn't do it for them).
I think most people who have booked anything you have to pay in advance for will probably be attending either way,.