Essentially the problem is with the iMX8 target SoC, it hasn't been released yet and the release has been held back to fix an issue with the produced silicon.

So at this stage its entirely out of purism's hands as to when NXP will decide to actually release the iMX8 properly. All the work purism has done so far as been for an iMX6 development board which isn't really up to the task of running a modern smartphone experience.