Le mans have opened the door for the F1 teams who leave, to enter the race next year, and the opportunity to help shape the techincal regs.
How about an open wheel class in the race?
How about no!
As for realistic Le Mans efforts, Toyota have already tried, and somewhat ironically considering their massively bankrolled failed F1 efforts, failed at Le Mans too. McLaren have won it (as have Mercedes, although their last attempt was disaterous!), as have BMW (using a Williams built chassis in 1999! Of course Sauber also won it in 1989 with Mercedes). Ferrari of course have had a presence for years, mainly in the GT classes. Brawn's had success their too with Jaguar in 1990.
Realistically will any of them enter in the near future - with Audi's domination I can't see any German manufacturers taking the risk.