Drysc just posted that the PTR is closed and that patch 2.4 testing has concluded. His announcement in totality reads: "The doors to the 2.4 Public Test Realm and Tournament Test Realm are now closing. We wanted to thank everyone for their participation and bug reports, and we'll see you on the live realms!"
WoW Insider will have extensive coverage throughout the day on patch 2.4. From the new gear, to class changes, to the new sights and sounds, we'll have it all covered.
This is a very strong indicator that 2.4 will be released tomorrow. I'll update as soon as official confirmation comes through that it hits the live realms tomorrow.
Updated 11:27 p.m. EDT: MMO-Champion is saying that 2.4 is tomorrow based on the above Drysc post and other hints from blues and GMs. Based on my information and my own experiences I am highly inclined to agree with them. However it's not official until a post or notice from Blizzard completely confirms it.