When is patch 4.21 scheduled to be released?

They've never stated any schedules for patching.

There's never been a schedule for them. A lot of the time they have been every two weeks or so, on a TUESDAY, however that's not always the case. 4.21 will most likely be next week however, as there is still loads of content being added to the PBE this week, since they haven't finished the current cycle.

I need to know too, but I don't think they've released an official date of its release. It'll probably be next week or two weeks from now.

"Patch 4.21 is huge! New champion, six new skins, a new game mode, lots of balance changes, texture rebalances and free healthcare. Patch 4.21 will be hitting live on December 9th, assuming there are no delays." http://www.newsoflegends.com/index.php/pbe-round-up-everything-youll-see-in-patch-4-21-30903/