You will have to get used to not having an OS upgrade if you have been holding on to a Pixel 4 for the past three years. The last guaranteed software update for the Pixel 4 and 4XL has been released. You can't count on anything else besides the usual round of bug fixes and patches. It's not clear when or if the last update will be a send off.
There are some family members who are still covered. The 4a 5G is safe until November of that year and the 4a is safe until August of that year. If you're a Pixel 6 owner, you can rest easy. The device line is the first to get five years of security updates from the company.
It won't be obsolete immediately. There are updates to the Play Services and apps that should keep the flagship running for a while. If you insist on a consistent update stream you should consider a new phone. The debut of the new device is convenient, even though it wasn't timed to catch device upgraders.