I love my iPhone 6+ and it was great when I first got it new 2 years ago. I came from an iPhone 5s, and going to the bigger screen was like night and day. It felt like a real "upgrade" if you know what I mean.
When the iPhone 6s/6s+ came out last year, I was tempted to upgrade, but I chose not to, because I didn't feel that there were enough improvements over my 6+ to warrant the cost.
I've been following iPhone 7/7+ news for months now, and I am having the same urges to upgrade again, but the other half of me isn't impressed with the so called "improvements" that have been talked about so far. My iPhone 6+ is certainly fast enough for what I do (photos, web browsing, email, social media, text messaging, voice calls, very light gaming).
I am tempted to skip this model and wait another year for the 2018 iPhone model (whatever they decide to call it). I just feel like the iPhone 7/7+ may not feel like a real upgrade. Time will tell though, as we all have to wait for the actual announcement to find out all the official features of the device.
Long story short, I'm still on the fence whether to upgrade or not from my 6+