That's about 94% of available tickets sold already. If no additional tickets are sold and students fill up their section 90%+ that would mean 59,000+ fans in the stands for the game. Given there is still 2 more weeks until game time I expect there will be 60,000+ when all is said and done and it could still easily be more than that. For comparison sake, here is how attendance has fared for comparable games/times in the past 7 years (I only looked at Thursday and Friday night games along w/ Utah games).

Thursday night game average: 57,338 - we've only had 2 of these recently and 1 was a season opener.
Friday night game average: 61,402 - 11 of these are included (5 of which are Utah St or Boise St)
Utah game average: 63,470 - only 2 of these over the last 7 years thanks to the 2 year break

Seems like we will easily exceed what we normally see for a Thursday night game. Attendance will probably be closer to what we see on Friday nights. It'd be a slight dip over if the game were on a Saturday, but that is somewhat to be expected given it's a late game on a weekday and most people will likely have work and school the next morning.