The physical dimensions of the battery can be smaller and still have an equal or greater milliamp hour capacity because of better chemistry of battery construction... How 'bout waiting to see some actual specifications before going off a rumor?
Then what is the point of the iPhone 6s forums? All everyone is going off is rumors!
Anyways I believe it will most likely be a smaller battery but like others had said it will be about if not slightly better battery life.
Still with that said, I still wish Apple would put bigger batteries in to last longer. Would love to go all day, or at least not have to charge at work.
Apple is close to the top with battery life to me, but I still would like better and I'm sure most would. My iPhone 6 last longer than most phones do but my 2 I have to charge my phone at work and it's not a huge deal but a nuisance because I work on an assembly line and no phone for a while then.
Like I said it's still better than most other phone manufactures. I personally would have been great with an iPhone 5s thickness if it meant having a bigger battery.
Just need to wait for tech to improve I guess.