The “evolution” of the iPhone could follow a path similar to that of the iPod according to John Gruber, who says new functionality will be added over time.
A simple trade-off between two things is like a seesaw: move one up and the other goes down. Think, say, of buying a new external hard drive - the trade-off there is between higher storage capacity and lower price. Or, say, how big to make a push button - bigger buttons are easier to hit, but there’s only so much space on a screen. Multivariate trade-offs are more complicated, but the basic gist is the same: you can’t have your cake and eat it too.
