you can try 'aptbackup' from cydia, or
iphone explorer, or ifunbox
i prefer to:
1) d/l the ipa's on the computer, replace and upgrade versions as they come out
2) double-click or drag into itunes; sync with itunes
maybe aptbackup even restores the app data and settings (or i.e. game saves), but i like to start fresh when upgrading firmware. remember not to restore from any backup when upgrading.