If you're desperate to get your hands on a Steam Deck, and you also happen to be a Steamworks partnered game developer, then you might be in luck, as Valve is now taking requests for dev kit versions of the new handheld.
Valve is now taking the requests through its Steamworks page, but you'll need to already register to the partner program to qualify. If you were thinking about just joining up and trying your luck, it won't be that easy, as there's a bunch of paperwork and a $100 fee, and that's just to get a chance to request one.
Essentially, you'll need to be an already trusted game developer to be in with the opportunity of getting one of these dev kits. If that happens to be you, though, then the dev kits are identical to retail units with a few minor differences cosmetically. If anything, they'll probably prove more valuable than the retail version in the long run.
Otherwise, you'll need to wait until the retail version becomes available. For those who got in early, the device will start shipping in December, but queue times are stretching well into 2022 at this point.