In brief: As the volume of Steam Deck pre-orders increase, Valve has started to give off some signs of uncertainty regarding the availability of its portable console. Initially, Valve was giving a three-month waiting period after reserving the console, but since then, the order availability has changed to a rather vague "After Q2 2022."
Anyone that's visited the Steam Deck recently will notice that the expected availability for the 64GB model has changed from "Q2 2022" to a less certain "After Q2 2022" date. This might be simply pointing to a Q3 2022 availability, but it could also mean anything beyond that. On the other hand, the 512GB model, which was previously expected to ship during Q3, is now scheduled for Q2 2022.
It's worth noting the expected order availability for the different models does change based on geography. In the UK, both the 64GB and 256GB models are expected to ship after Q2 2022, but in Europe it's the 256GB and 512GB models that are scheduled to reach customers after Q2 2022.
Considering how far off we are from Q3 2022 and beyond, it looks like Valve is just being cautious about the availability of the upcoming PC-based portable gaming machine.
Whether it's the ongoing chip shortage, the reserved chip stock to the console is on its last legs, or just the uncertainty of time, you better be prepared to wait for the Steam Deck if you're planning to reserve it.
There's also the issue with scalpers pre-ordering Steam Decks to resell it. eBay has removed these listings, but scalpers can always use other channels. In any case, we recommend you not to buy from scalpers.
As for anticipating the expected order availability of the 512GB model in the US, it could come to Valve now having enough data to check which models it should prioritize, balancing production accordingly.