Should I upgrade my iPhone to the 6s?

While it was with mild amusement that I learned this morning of the Apple iPhone 6s release that is imminent, I was a lot less impressed when I went into an Apple store here in Sydney a couple of months ago to ask for screen protectors for my iPhone 4.

This is the thing. I don't see a lot of reasons to upgrade to a newer version of the device - mine was purchased in 2010, almost six years ago - but it also makes me a little nervous when I think of the risks. I don't want my phone's data to be made useless because I missed taking a critical upgrade path. I have more than just photos on the phone and it's about a lot more than just screen protectors that fit. What is most precious to me are my contacts. I would be devastated to lose access to these. Given, they are also stored on my PC using iTunes, but still ...

To be honest Apple must not care a lot about what I want from my iPhone because I'm not that guy with a sleeping bag queuing up outside their city store for days in advance of a new offering coming on sale. The only thing I can really see motivating me to upgrade is to get better battery performance. As I wrote back at the end of April, you only get about 15 minutes' broadcasting time with this phone. More recent versions of the iPhone deliver better performance in this regard. But apart from that one quibble with this (relatively) ancient device, it does everything I need, and a lot that I will never need to do.

Quite honestly I don't see a lot of need to upgrade but I'm always open to persuasion. Can you think of any reason why I should take the plunge and invest in a new device to replace this old thing with?