I'm still considering an iPhone 6+, but to me one handed use is not a concern. I don't text one handed because I don't text while I drive, and I also don't type while I walk. I will text while I'm standing like when I'm out shopping, etc. but I'll automatically go to landscape mode on my 5S. In fact, I do everything in landscape unless the app I'm using doesn't support landscape mode.
Considering I have x-large hands (evidenced by glove, garden glove purchases), the iPhone 6+ may slightly enhance my one handed usage. The keyboard being larger while in regular mode may help me out. I doubt to the extent that I'll use it often, but maybe in a pinch. I already view my iPhone 5S as a small iPad so I don't think the iPhone 6+ will be much of a change for me.
I'm really concerned about putting the 6+ in my pocket and having it dig into my leg or something. That'd be annoying. I'm going to wait until I can see one in the store before I make a final decision.