Unless you're buying it outright I'm not sure what the issue is. Nobody knows what the iPhone "5" will look like or when it will be released. Putting stock in rumours this far out is just plain dumb.

So, get an iPhone 4S if you want one. If you're on Verizon, ask them about unlocking the SIM card slot (which they don't use, so they should be willing to unlock it if its not unlocked already) so you can use a GSM micro-sim in whatever country you end up in. Verizon uses CDMA which isn't covered in other countries so I can't see where they would object, since you'll be paying their bill just the same ...