So should I wait for the HC Compendium or just buy the HC Volumes?
Buy the Hardcovers.
I've owned every single version of everything TWD. Singles, trades, hardcovers, omnibuses, compendium. Hardcovers blow everything else away from an all around standpoint. They are the best value and more importantly, the most comfortable version to read and will keep nicely.
The omnibi, although they are nice, they are too big to read comfortably. The compendium is even more awkward and that bible is probably only going to be worse. If you want something that you can sit on the couch or in bed, the hardcovers are perfect. When you get into the omnis and compendiums, you don't have much choice other than to read them at a desk if you don't want to leave a mark on your chest or mess up the book.