Ah, thanks... that helps.
Given that, I don't think it is worth upgrading to a 256GB 9.7 iPP at this point in time. First, you will get killed on the resale of the 128GB Air 2. Resale values have seriously dropped on iPads since stores have started regularly discounting iPads. The hardest hit on resale have been the higher capacity models.
Second, there are some serious possibilities of new iPads being released/introduced in March 2017. One of them is supposed to be a 10.5" iPad Pro... smaller bezels but in the same form-factor as 9.7. You might want to wait to see what shakes out then.
Third, this is just my opinion, but I never had a good feeling about the 9.7 Pro. Something about the 2GB RAM, $100 price increase, and the timing of the release just felt a little "off"...like maybe there won't be a proper update to the 9.7 Pro. This is just my feeling so it really is not important in the discussion.
I too like to have all of my media with me on my mobile device, but there is no device out there that comes close to what I would need. So I've had to deal with the situation, using smart-playlists for syncing music, and manually selecting videos, comics, and other media to cover a wide range of moods I might be in.
As a temporary solution while you wait, you might want to consider the
RavPower FileHub. (
@M. Gustave turned me on to it) $33 at Amazon, and another $30-40 for a 128GB SD card to insert into it and you'll have another 128GB storage for use. It is no way as convenient as having all 256GB onboard, but I've been testing this combo out (as a solution to my mom's "iPhoto storage creep") and it works great.