What will you do if Apple do make it bigger?
Well... of course I'll bail on Apple and get an Android or MS based phone!
NOT!
Personally, I don't think they will. I think they are more concerned about all their customers - men and woman. Large and small. They know overall feel in the hand for all their customers is important and that it's important that it slips easily in your pocket. I don't think anyone here can argue that Apple is one of the best, if not the best out there right now, at product design. This does not happen by accident... I'm sure they test and try many variations to get where they're at.
There are more important things they can do than mess with the best smart phone screen on the market.
No matter what, there's always going to be competitors with something that's bigger or more. But again, it's not about any single thing that makes the overall product. It's the overall product that makes the iPhone so great.