I think your idea of riding what you have and then decide what you want/need is a good plan. Here is my situation/bike choice/reasons:
I ride around the Seattle area (Cascade mtn range). Most of my rides consist of a long-ish fireroad climbs (with some mixed singletrack) followed by a descent on fast, flowy single track with some rough/rooted stuff, some jumps/drops and such. So for me I wanted a bike I could climb, but with a bigger focus on the downhill portion of it. My thought process is sacrifice a bit of ability on the uphill to gain a bit of ability on the downhill side of things.
I have been riding a 27.5 5+" travel bike. It is a bit more slack than a dedicated XC bike, but I want more stability on the down. I have been very happy with it. I am running a 1x11 Sram drivetrain and I can make it up everything no problem (a 44 tooth cassette helps!). My lady rides a 5+" 29er and is in love with it. When 29ers first came out, they all felt really tall when you were in the saddle, everything just seemed to be higher off the ground. They have figured them out and the 29ers of today are low slung rockets. She rode a 29er trail bike at whistler and I couldn't keep up with her on a 26" DH bike. They are super functional now.
I would say don't buy a 26" bike. I think they are going the way of the dodo, so you might as well invest in the future. I think it is going to get harder to find 26" stuff in a couple years (like rims, tires etc). I could be wrong, but that is how I see the industry heading.
For travel, I wouldn't bother with anything more than 5" unless you are really hitting the gnarly stuff on the regular. The bigger wheels coupled with the 5" of travel really make for a smooth ride. That being said, a really tall friend of mine is riding a 6" 29er and says it is the best bike he has ever owned. He rides similar stuff to me.
One thing you def should do is demo all sorts of bikes. Most bike shops will have high end demos for people to try. Try them all. See what feels right, that is the ultimate decider. Also, at the end of the day, you just gotta 'run what ya brung' so there technically can't be a bad bike buying decision.
The one thing that isn't up for debate, however, is the dropper post. Whatever bike you get, invest in a dropper post. Best mtb invention since, uh, sliced bread!
Good luck & let us know what you get!