I would love to see all/any of Porsche, Le Mans or the WEC in AC but not really onboard the hype train so far.
AC getting Le Mans would make sense if the ACO had laserscanned the circuit so could sell it to anyone (like what was done with Nords), but from what I have read I think the iRacing data came from their own team going there. Plus would Le Mans for AC make sense with no day/night transitions, no driver swaps, etc...
I think a WEC license would be too expensive and TBH the WEC deserves it's own sim rather than just a WEC pack or two for AC. Would iRacing have gotten into bed recently with Blancpain if a WEC license was on the table?
So Porsche maybe? Seems like it would be expensive at this stage of AC's development when they can only sell EUR10 DLC. Would be a good license to get for AC2 though.
Kunos already have licenses from Toyota and Audi though so my bet would be the TS050 or latest R18 either of which would be cool.