Wait for the 6s...actually you might want to hold off because the 7 is right around the corner.
Probably won't get a 5s until October, so buy the 5 now.
Although some rumors are saying Apple is going to announce something this Spring. But I think that will be a new iPad or a t-mobile iPhone 5.
I don't really think 7 is gonna all that better than 5 let alone 6...If the original 4 was the Conroe then our current gen phones are already the Sandy Bridges of phones. Can't really make the screen bigger, DPI any denser, battery life any longer, and even the most promising SoC part are hitting silicon walls.
I'm bumping BlakeBang minus all the Lumia and S3 stuff... What are your reasons for upgrading? The variation in performance between the 4S and 5 isn't that extreme, so unless you just want an iPhone 5 I don't see any reason to upgrade right now.
I have the iPhone 4, and it's definitely showing its age. I would love to upgrade to the 5, but I pretty much require a jailbreak to use the iPhone, so the 5 isn't an option. So while I've loved the 4, it might end up being my first and only iPhone. I'm just sick of getting bogged down waiting for JBs. That's only going to get worse as time goes on.
As far as I know, even the latest and greatest Android phones like the Droid DNA get rooted very quickly. That's very enticing to me.
If you want your 2-year upgrades to have the biggest bang for your buck (as well as being noticeable from the previous version), upgrade on full numbers, not "S" versions.
Get the 5.