Supposedly there will be an additional Porsche team to be announced at a later date (probably Petit Le Mans weekend).
John Dagys' notebook following qualifying for Sahlen's Six Hours of The Glen...
sportscar365.com
My guess is M-Sport since they are still planning on doing some IMSA races despite missing this weekend.
Wayne Taylor has said his goal is to expand to 2 cars for '24 as well so that's another possible entry. ACO has also been lobbying on behalf of Glickenhaus so who knows what will happen there (he's also threatened to sue IMSA but I can't see that ending well for him).