full GNU/linux userland running atop Android...

"if" it ever happens...
"if" it ever becomes truly viable...
"if" it doesn't end up being a "one-off" due to Android liking to change things ...making any possible working model ...useless...(more likely a scenario)

then sure... I would definitely consider an Android phone ...purely for the ability to subvert it...and use linux.

but as you have mentioned x11 being a presiding issue...
I doubt it will materialize..
perhaps in the future ...something will come about.

the 4 biggies are that
Android uses a hard modified version of the Linux Kernel
Android uses BIONIC as it's Standard C Library instead of GlibC
Android doesn't include the GNU coreutils
android-eabi is different from the gnu-eabi

conquering these issues is very unlikely..
wiggling around these issues (more likely) would have to happen.

currently ..just having a bare bones terminal to tinker in...on an android phone..
isn't enough for me to even consider it as a daily use alternative.

A single device that is both linux comp and phone is ultimately what I desire..
I can tolerate for the time being needing an android phone purely for calls and telegram and translate..
(shortly when she arrives ..haven't seen her in a year now...and she is due to arrive on the 3rd of October.. I will be edifying my girl on the use of irc ...and it's inherent translating abilities...then will be introducing her to a N.I.T. ...and that then negates for a time...staves off the need... to use a damn android phone...)
and use my N.I.T.'s for proper usage...

2 devices isn't my preference...
especially one of them being android.
that will shortly be temporarily remedied...concerning android.
then it will be using my n900's until the zerophone is out.

For me ...
If it must be 2 devices I carry ..
supported and current is the only option for the investment of time effort and money...
Switching to the pi phone and migrating to a franken-pi for my mobile work, puttering and fun is a better alternative for me...
than now ...just tolerable..aging ...n900 and lugging about a laptop for convenient browsing..
or the intolerable android and a laptop...

eventually (and not too far off... I would imagine) I will only need 1 pi device for my needs ...the headway the pi has made over the years is impressive...and I expect it to only improve..