So I've got a 6 plus that I've had since they first came out. Battery is pretty terrible and this point and certain things are just slow. I've got a brand new unopened 6s that I could switch to if I wanted. Should I switch to the 6s or sell it now and hold that money until the 7s/8 comes out? Or should I switch to the 6s and then sell it before the 7s/8 comes out?