The database I am working on right now has records being added and removed by the 10s of thousands and because of this there are gaps in the auto-incremented key hundreds of tho
I don't know what the growth rate of your autoincrement field is, but it should be simple math for you to estimate when you will hit the 4294967295 limit.
If you still feel that you need to do something, you have the following options:
On a separate note, I sense a poor decision or two somewhere earlier up the line here.