These forums are great for exchanging ideas, etc... but I don't think you will get any concrete answers here considering that it seems to change by the day (as far as what is getting built when, what the shortages are, etc...). I feel your pain though, I would like answers as well.
If it helps though, I can give you my guess....
I think the hangup may be spoiler related. I ordered right after Thanksgiving (premium GT, manual, IUP, upgraded rims, side airbags, spoiler delete). About a week ago my build date was the week of 1/3. I called this last Monday and again yesterday, and now it is the week of 1/17. It is a pretty good guess that it might be pushed back again.
I wouldn't put a whole lot of faith in what dealers tell you. Some know more than others.
Good luck