Impossible to say unless you want to do it yourself 😅
The basic Linux kernel patches will be in the next release, and then it depends on when the mobile Linux distros upgrade the kernel.
But I think entusiasm for the FP6 is relatively low in the mobile Linux space, as they removed usb3 and display out from the hardware. I suspect the FP5 will remain the best supported one.
The FP5 SoC is a industrial IoT chip, so there is actually longer term support from Qualcomm which is IMHO better for Linux use.