Root Possibilities

I know I'm getting a little ahead of myself but I have an upgrade coming soon for my contract and have been heavily researching all the phones out there at the moment. I really like the idea of the z5 premium with obviously the 4k display, the ip68 rating, and especially the microsd card slot. My one question is that, coming from my most recent phone, the Verizon Note 4, I was very dissappointed with the fact that I could not root the phone and could not utilize my favorite form of android, Stock, Pure Android.

So I guess my main question is, considering my lack of familiarity with Sony devices, I was wondering what the chances that I could ultimately root and install an "almost" stock ROM on the Z5 Premium were?