Gif, I've also considered buying the mega bundles, but with you releasing more packs all the time I've held off since I dont have a project where I'd use them yet, so waiting makes more sense.
Some other creator's bundles I've purchased on itch do offer the ability to get new updates via the "claim" mechanism. I'm not sure how that works exactly from the creator side. It would make the bundle more attractive if we knew that by buying it now we don't miss out on all the awesome stuff you are releasing later.