I think it will be a case of some (alleged) diehards not returning, but also some new ones will be created.
Obviously next years crowd will be back to around recent numbers, although with extra brands in HyperCar and the switch to GT3 (boo) might bring some new fans or retain those that are new this year.
It would be interesting to know if there has been / will be an increase in ACO members, with the earlier onsale option for members it was certainly an extra benefit of being a member for this years race.
One thing is certain, well as certain as it can be, there will be a race next year.