My iCloud's nearly at its 5GB capacity, what happens to my iCloud email account when it is?

I have two handheld devices synced to my iCloud account and my iCloud email address.

Between the three of them they are nearly 5GB.

So my query is, what's the scenario when the combined total goes over 5GB and I can't afford to give apple more money on a monthly basis for more storage space?

Obviously I can easily create another account for to sync my handhelds too, but I don't want to get to the point where apple stops me from receiving / sending any more email because I'm over my storage cap! If this is going to happen it makes sense for me to switch email accounts asap!

(I should explain my work means I get sent > 200 emails a day most of which have hi res emails and some of which have mp3s attached so it wont be too long to hammering on the 5GB door max door!)

Thanks.