I can confirm a large number of Teensy 4.0 will be made in December. We just heard an update from NXP that the chips are inbound, and we've queued everything else up so the production can begin when they arrive. I know December feels like forever, today being at the end of October. If everything goes *really* well, there's a chance some might come in the final days of November, but usually the US Thanksgiving holiday throws a money wrench into the production process, so at least this far out I'm reluctant to promise anything at the end of November. The schedule will become clearer in a few weeks.
Generally speaking, PJRC starts pre-orders only a matter of days before we are certain production will complete. Or the first portion. We're doing that now for Teensy 3.5, which is a small all-at-once build coming in just a couple days. For a large build like Teensy 4.0, they don't all finish at once. Some roll out of product each week. Especially when we have other boards in the production queue, they tend to get interleaved. The upcoming Teensy 4.0 batch is large enough that it will probably take every week of December to complete.
There's a couple reasons we allow pre-orders only shortly before well confirmed ship dates. The main factor is limitations with credit card processing. Like most small companies, we use a credit card processing service which never shows us your card number. When you place the order, your browser sends the card number directly to the service (today, that's Intuit, though we're planning to switch to another service someday) and the card processor gives your browser a transaction number. We get only that transaction number and the info needed to ship your order. The service reserves funds from your card at that time. But the charge is made when we ship. The service only allows the transaction number to be used once. But the most important part is the transaction automatically expires, usually after 1 week. For card security, this is great news. The only info which gets stored on PJRC computers is used or expired transaction numbers, so even if a thief were to steal every last byte of PJRC's data, they can't possibly get anything which lets them steal your credit card. But it also means we can't delay charging your card. We almost never charge a card until the order gets into the shipping queue, which usually means it will ship that day. The other factor is a lot of pre-orders really makes everything more complicated for us, at the worst possible time when we need to focus on getting as many Teensy boards tested and packaged. PJRC is only a small company, just a 4 people including me and Robin, plus a couple local contact manufacturers who do all the soldering. Many of the limits we have are because we just don't have a lot of people, and the pre-order limit only days before shipping is definitely one of those limits.
Larger pre-orders higher than the credit card charge max aren't as much an issue. If you know you'll need 100 or more, and you really want to pre-order to get early in the queue, just email me directly. Such pre-orders are really just a place holder. Robin will contact you only days before we are sure the products can ship, to arrange payment (usually bank transfer for large orders).
For a small order, just keep an eye on the Teensy 4.0 page. I'll post new updates as events unfold, with more specific info as we become more certain of exactly when they'll complete production. When you see the updates promising a specific ship date, mark your calendar to check the page about 4-5 days earlier, as that's when we'll start pre-orders.
As we're doing now with Teensy 3.5, the first couple weeks will probably have a limit like 10 per person. If you're doing low volume production and you *really* need more than 10, just email me with details (but please, when the website is taking pre-orders). The initial quantity limit is only to limit ebay scalpers, not to hurt people who really are using Teensy. If you can mention your prior orders and give me even a little info about your product, we'll relax the limit for your order. By mid-December we should have plenty and distributors should be getting them back into stock, so the quantity limit is just a short term thing.
Beyond December, we're expecting a large number of chips for Teensy 4.1 in early January, even even more chips for Teensy 4.0 later in January. Predicting the future is always difficult, but my hope is NXP will keep providing chips at these levels and these painful shortages of 2022 will be a thing of the past for 2023.