They announced for now hours at AK until June will be extended. After that it's pretty much just stay tuned. But there's no reason for them to not keep the extended hours. Night safari, rivers of light, the hours will be extended. I would anticipate closing time to be around 11pm then, then probably 10pm later in the year.
I just posted in yet another thread on the night time hours that I suspect/wonder if they aren't holding off on the Aug/Sept hours till they know if RoL will be ready or if they'll have to stick with the fill in. Maybe RoL will have more shows than Jungle Book will? I haven't really checked the schedule for it just yet, still waiting on AP rates for Aug so we can book our next trip. Then I'll start looking