no you not lose anything,if you read the previous comment ignore it,the answer was inaccurate,updating does not delete anything......you might like to back up just to be on the safe side.
You however will need to Re-Jailbreak as just like any ios that has a jailbreak.
Also backup in itunes just incase something goes wrong.
Also get a program called pkgbackup as it will Backup Your Cydia apps, if you choose not to, you will need to reinstall all Cydia apps and tweaks you use.