FWIW,
I have the Tab S 8" tablet and I LOVE IT. The screen is amazing, it is light, fast and even though I have the retina mini 2 the Sammy device is my go to.
They are on sale now at a lot of places so you can get a good deal on them. I am usually one of the people that pants at new tech but I recently bought the iPad mini 2 because I wanted to replace my iPad3 and give it to my parents.
If it is not your main device, getting a slightly aged (and the Tab S ain't that old) then it may be a good buy for you now rather than waiting.
As for the data plan, I tethered it from my Note 4 when I was on course for a month (don't have unlimited data but it worked great). I also like the fact that if you are on wifi with both devices you can basically ghost your phone onto your tablet and not have to carry both around as your tablet becomes your phone.