My 6+ has this issue, and I went to the Apple store yesterday, and they gave me some BS answers.
Took it out of my case/bumper, and set it down, and they said it didn't wobble and it didn't look bent. I tried it on multiple surfaces at home and work, and it for sure does. Then I mentioned that it was a known issue that these bend, the lady said that it's an issue in the media, not for Apple. I then found a table that it did wobble on, and they the lady said it was because of the camera lens that slightly protrudes out. But it's not on that axis, it's on the opposite one where it could not be the camera's fault. I told her I didn't have this issue when it was new, so it had to have become like this.
The lady then said that she would go get one of their phones to compare. Their phone was actually worse with the wobble. She said that it's considered physical damage, and the warranty won't cover it, and a replacement phone was $329. I started laughing and said that's $70 less than what I paid for the phone. I said I had insurance through my carrier, and I'll see what they charge.
Needless to say, I'm not a happy camper. I only keep the phone in my front pocket, I don't wear skinny jeans or anything, and I don't do anything with this that I didn't do with my iPhone 3, 4, or 5, so obviously there is a issue with the 6+.
I'm thinking of sending Apple an e-mail explaining my situation and see what they say about it.