The 5 is not going to be lighyears ahead of the 4, so I am sure you will be fine if you do not feel like you have to have the 'latest and greatest'. Hell, I am still using an LG feature phone while I wait for VZ to come out with a cheaper data plan. Then I will get a 4 as I am sure the 5 won't be woth the wait.
all the iphone 5 is is a better camera (i dont care im not a photographer) and it faster but the iphone 4 is fast enough its not like im going into a fastest iphone competition