Due to the new Hypervisor exploit found in specific Xbox 360 kernels (see news article), 360 Homebrew development is in progress.

http://www.xbox-scene.com/xbox1data/sep/EEZFpZuFVFfajVjLfN.php

The Hypervisor exploit was just the thing hackers needed to push them into homebrew development for the 360. I don't know how well it will go over, though. The 360 is pretty much tied to XBL, so the only way 360 homebrew would work is if they found a way to stay connected to XBL while running it, and finding a user-friendly way to install it.