The wishlist is a great tool and your best bet for getting a ticket to the really popular events. Definitely use it! But if you don't get into something, don't worry, there's plenty of other stuff.
Our first Gencon, we didn't purchase any event tickets until about a week prior to the con. There was a ton of stuff sold out at that point, and I wouldn't recommend waiting until that late to get started, but there was still enough open events that we were able to find things to enjoy.
More events will be added after the Wishlist processing, too. We just use it for the things we really want to do and then come back from time to time and check the database and grab a handful of other events as we see things that interest us.