Is the iPhone 5s forward thinking enough?

I have the opportunity to upgrade 1 year early from a 4s to 5s for minimal incremental cost. It would be a no brainer choice except 1) 4s is IMO a better design 2)The "S" iphones are not very future proof. I don't want to be in deep buyer's remorse when the 6 come out game-changing. Do you think the 5S is future proof (2-3 yrs) if screen size is not a major factor?