Okay, folks — I've updated to the #FreeBSD 15.0 on my #Thinkpad X220 
The process itself completed without any problems — I used freebsd-update as usual. After first reboot (kernel updated, userspace not updated) I met the strange blinking of display, while the second "freebsd-update install" was running in the text console. But after update was fully completed, this "problem" was gone.
After update, i915kms refused to load, system says that it is already loaded or compiled into the kernel. So, there are no graphical interface (possibly I should run "pkg update" or install drm-kmods from FreeBSD-kmods repository 
)
And there are no networking with iwm and Intel AC 8260 (possibly, it's time to finally switch to iwlwifi, lol)