Well that answers that question. Once training started yesterday I found myself wondering if the Timbers would just end up training for the duration of the off-season for the next few years at adidas HQ. It made sense given that adidas is a local-ish company along with the current deals adidas has in place with the league.
In actuality, the real plan for the future isn't that far off from what I was originally thinking, although it's not going to be at adidas HQ. Instead it will be at an adidas sponsored 6,000 sq. ft. indoor facility with locker rooms and office space for the team in addition to a natural grass field reserved for private Timbers use and a turf field for public use.
The new training facility isn't due to begin construction for another few weeks and won't be complete until this summer so, for the time being, the Timbers will probably resume pre-season training at adidas HQ. Upon completion the Timbers will then train exclusively at the new training center and PGE park.
Oh and for those curious the new training center will be at Tualatin Hills Park & Recreation District off Highway 217.