The 2020 theatrical release calendar is getting even slimmer in the wake of the announcement that Regal cinemas are temporarily closing, although AMC Entertainment says it will remain open. Warner Bros. said late Monday that its sci-fi pic “Dune” will now open in October 2021, instead of this December. The studio also pushed “The Batman” to 2022 and moved up its “Matrix” sequel. That leaves a mere handful of big films set to still open in 2020. The nation’s largest theater chain, AMC, plans to remain open and cited its shortened theatrical window agreement with Universal as a reason.