A challenge to this sort of suggestion is that the device OEM rarely controls all the software which goes into a device. There are third-party modules, hardware drivers, and more, which are also components. Then there are patents.

Either the escrow would have to apply to all software on the device, regardless of whether owned by the OEM or third parties, or OEMs would be required to vouch for all the included software.

I'd prefer the former myself: multiple software and patent assets can be combined, but on support EOL, all those become public domain.

Build / release / update toolchains must also be included.