Exactly this for me, too. I don't hate my 6 Plus. I have reveled in the glory of its large screen many times. And I have it encased in a slim sleek wallet case that makes it as nice to hold and carry as it could possibly be to hold and carry a phone that big.I'm happy with my IP6+ through I've come to the realization that for me, and my usage habits its just too big. I end up selling it this summer and get an iPhone 6s/6c that will presumably be coming out this fall.
But when I need a big beautiful screen I have my Retina Mini for content consumption and web surfing. My typing is horrid no matter how big or small my keyboard is so going back to a smaller keyboard won't hurt anything.
I recently got the Apple Watch. It's gotten me fired up about getting up and moving again after an overly long winter as a couch potato. I don't want to lug a giant phone with me on hikes anymore. Yeah I can do it, but I don't want to.
So barring announcements or solid rumors of an even smaller iPhone with good camera in the horizon, I'll be downsizing to a 6s. With the Apple Watch the phone has become less important as some wonderful all-in-one-device I may once have envisioned and less compelling to me than the tandem team of watch and phone and IPad together, each playing its role for me in an optimal manner. To get my optimal team I do feel I need to downsize one of the players and it will be a near perfect Apple experience for me.