As much as every backer would like to manage their own expectation, you will have to be realistic. They are working on some real issues like e.g. the 90 Hz refresh. They will not know today when (if) they can get that resolved. So how to schedule a final delivery date then ?
And imho we should factor in a second element - Pimax may be convinced by beginning of January to have a good enough prototype & design, but the proof of the pudding (hopefully) comes with CES 2018: once the final prototype is being demoed and users experience flaws nevertheless, Pimax will be expected to address these (where it makes sense, may be expected to improve in order to provide for the desired and advertised performance).
So expect any realistic statement on the delivery date only at the end of CES 2018, if everything seems fine by then, or if not, only at some date after CES 2018 when Pimax announce, that they have solved the remaining issues and are gearing up production.
Patience is what we will all need to apply here, nothing we can do about it. Pushing & bugging them in the last weeks for such confirmation doesn't achieve anything but to get them to rush out a flawed product before it is mature enough.