The cases are actually worth a lot, it may be worth it to buy the pass for $2.
Then again, there are hardly any on the market so it must be a pretty rare drop.
They'll drop, just like the Gun Mettle cases.
Also just like the Gun Mettle cases, if you bought the pass for whatever reason, sell that shit while the selling is good. No crime in taking advantage of stupid traders who must have the shiney new thing right away, and pay a silly premium for it. Once the crates actually start to drop in any appreciable number (mostly from those trying to get in on fleecing traders as quickly as they can) they'll be easily had just like the weapons cases, and then I may unbox a couple, because the new invasion effects do look pretty baller, imho.