Those that queue before 9am are generally people wanting to get a good VQ number for autographs, I wouldn't imagine that even in a massive queue you'd miss your shoot. There are usually stewards outside monitoring the queues so I'm sure if you were close to your shoot time and have yet to make it into the venue you could have a word with them and they'd get you in. Although I would suggest getting to the venue before doors open to minimise worry about the whole situation. Hopefully that helps? Mods, if any of the above is incorrect feel free to edit. I'm only talking from personal experience.
Thank you guys!
We'll be there from 8 am as latish, as we wouldn't like any inconvienences to get in the way of our photoshoot and great experience at the Comic Con, however I'd appreciate some clear info about this whole thing from admins, mods or showmasters themselves!