So you just recently upgrade to the 4S? Yeah I'd probably wait to see what they do with the 5S. I made that mistake when I got my 3G in 2009. A few months later Apple release the 3GS. I was kinda upset about that cause my 3G quickly felt out of date. By the time the 4 and then 4S came out It really felt slow and old.
I have had my 4s for 20 months. After 20 months, I am eligible for an upgrade, even though my contract isn't over until October.