The newest iteration of the Gear VR, iirc, is more or less the same as the 2016 version, so unless you're upgrading to the S8, you should be fine with the 2016 version. It does have a significantly larger FOV. I used to think it was only a slight increase until I had to go back to the white version recently (my wife had my 2016 version in her car) and was taken aback by how much more limited my view was.
The S8+ should work as well; like @
Blakey_nz said, it would fit better in the 2017.
If you're upgrading to the S8/S8+, I'd just take advantage of the current promo and get the 2017 Gear VR and controller bundle for free. If you're not eligible and want to save a little money, maybe pick up the 2016 version and the controller separately and see if it fits okay with your phone. If you're not worried about money, but instead just want the best experience, go ahead and get the headset and controller bundle for $129.