I've been hounding authors for super high-level adventures as well, and starting with May's issue (#122) we've got a menace from Mike Mearls for 18th-level characters. And a few issues after that we've got a high-level one that should prove quite popular.
And to top it off, we've got an acutal epic-level adventure scheduled for early summer! It's called "Quicksilver Hourglass," it's for 30th-level characters, and it's gonna make a lot of PCs cry. We'll include some notes and tips on how to adjust it down to 20th-level (and all the levels in between), but it's definately going to be the highest-level adventure we've ever published. Just the thought of editing those stat blocks makes me giddy!