Will probably get if it's iPhone 5 with bigger screen. Proc bump is a given and honestly I'm totally content with my iPhone 4 for now.
If its just a 4s with same form factor but better proc only then I'll pass and keep my iPhone 4 until a proper full revision to 5 comes along and knocks my socks off with must have goodness.
Wife is about due for an upgrade though and I'm not sure she'd want to wait another year for a 5 if it doesn't happen today. She's on a moto droid 1 at the moment which sadly feels so sluggish and outdated already.