Hi there, I'm the guy who posted the updated sourcemod gamedata for the update.
I got trusted with early access to the game and I've been able to inspect some of the binaries to find out about what may break sourcemod plugins/extensions.
I can't talk a lot about the update, but in hopes of helping this update go smoothly,
I wrote up some notes about the major breaking changes I found, which is available as a Github Gist: L4D2 2.2.0.0 gamedata fixes.
If you make extensive user of vtable offsets or memory address reads in your gamedata you might find useful information here to get your plugin ready.
Also, there have been a number of bugfixes in the game, for things like Charger Chest-bumps. So you might find that some plugins become redundant after the update drops.
I apologize for the selection bias of plugins I've tested, but hopefully some of this is generic enough to help.
I'll be around on the SourceMod discord today and can try to answer more questions.