If you are able to keep your current device until summer, do it. There will be a new iPhone during the summer. It may not be a completely new and unique device, but it will be an upgrade from the current one.
There have been probably over 20 threads on this subject. It's been beaten into the ground. Phil said during Macworld that the product cycle for the iPhone is every June/July. Beyond that statement, there is no other solid information.