If it releases at GenCon, why would you expect them *not* to use it at GenCon this year?
I did not say that they would not use it this year, certainly they will. However, as it is just being released, they will probably not have the resources, i.e. GM's, players, etc., to fully roll it out as their main focus.
Two years ago when they rolled out Starfinder at Gen Con there was limited scheduled play (Gen Con tickets), but they had a line to wait in for 1 hour demo play games. The GM's were not fully prepared and I knew more about some of the rules, than some of them did. That is simply because the rules officially came out Thursday of Gen Con.
Last year, they had a full assortment of Starfinder games with very well prepared GM's and players as the rules had been out for a year.
Last year, they rolled out the Pathfinder 2.0 playtest rules on Thursday of Gen Con and they had similar 1 hour demo game sessions. Again, the GM's knew the rules, but not as well as you would expect for normal Gen Con games. Now that it has been out since last August, everyone is much more familiar with the playlets rules. The question is how much will the 2.0 rules differ from the playlets rules?
I am just making assumptions based on past experience, but as this is a playtest becoming a new edition, maybe they feel everyone will be familiar with it enough to roll it out en masse. I still think this will be the last full year of 1st edition at Gen Con.