It's probably a one-shot deal, since Hasbro and TRU aren't going to want too much non-movie stuff around when the Preview toys and such are released full-force.
But Soundwave shouldn't be entirely sold out by any means. TRU's online store, yeah, but others are out there (BBTS, Action-HQ), there's still other TRU brick-and-mortar stores reported to have them, and if you absolutely must bite the bullet... eBay.
The collectors most screwed now are the kiddies and other people who don't have easy access to more distant TRUs to get Soundwave. All I know is, when you see a desirable exclusive available for preorder, you're probably going to jump on it.
All I have to worry about is getting some minty cassettes to go with my shiny, reissued Soundwave.

[/rubs_it_in]