Just upgraded to 2012 R2 CU4 from SP1 and having the same issue. Task Sequence won't finish and doesn't error out after the SCCM Client install step. It doesn't even try any steps afterward but any new image machine will stay stuck in "Waiting to Install" with all the files already downloaded in the cache. Not sure what it's waiting for. No Maintenance window set on any collection. I've found another post from mshaboboo with no answer to this problem as well. Anyone ever get this resolved. Not seeing any errors in any logs that seem relevant.