I would hope the battlegrounds cards would be legal at gen con. They will have been street legal for almost a month.
That is presuming they are out this upcoming week as planned.
I wonder if there shouldn't be some sort of moratorium on the use of cards... say, one to three months after publication... for their use in tournaments.
I'd hate to think that some people might have access to particular spells that others may not (due to potential distribution or underproduction issues, for example). Even if there are no such issues, I'd think that it still might be better to keep some players from having to face the next "mandatory include" without having been able to afford to purchase the set as soon as it comes out (say, until the next pay check), or the understanding of how their current strategy may be changed due to making cards that they have never seen available.
Unfamiliar cards in play also may tend to slow down tournament games as the players who have never seen them before take time to look them over as they are played against them... and work out strategies on how to deal with any surprises contained in them.
Also, we probably end up playing against play-testers or others (for example those on OCTGN) who may have used (or at least studied) new cards for months prior to their publication.
If the idea is to encourage serious players to purchase products immediately upon release, then it works better if you allow cards from products released up to the day of the start of the tournament. This also may serve to frustrate others and keep them from playing in tournaments... or perhaps at all.
Just a thought... I can live with it either way. For my purposes, I just need to know how to finalize my tournament book sometime before the day the tournament starts. (Thanks for letting us know that the decision will be made very soon now.)