Will updating my iPhone 4s delete anything?

I have an iPhone 4s that needs it first update and i need someone that i completely sure. I was about to update it and it said the following There are purchased items on the iPhone "Black Rose" that have not been transferred to your iTunes library. You should transfer these items to your iTunes library before updating this iPhone. Are you sure you want to continue?
Will that delete anything? I need some one that is sure and has done this b4 NO guessing!

I have an iPod, so this is probably the same case.
It will not delete anything UNLESS you have transferred all of your things to your computer. I thought it was going to delete everything on my iPod, too, when I updated it, but it didn't. Some things didn't even transfer on to the computer and it stayed on my iPod.
To transfer things from your iPod onto your computer, simply plug it in to your computer, iTunes should open up, and when it's syncing it will transfer everything. Then make sure it is all on there, and update it.
Nothing will be deleted, don't worry.

Just before you update select File top left of iTunes screen then scroll down and select "Transfer Purchases from "your iPhone name" once that is complete you can update your iPhone with confidence before the up date commences your iPhone is backed up to either cloud or computer depending on your choice on the back up panel below the update panel.
Now be prepared for the up date to take quite a long time so be patient and resist the temptation to switch off there will be sometimes what seems no activity for long periods but rest assured all will be well, make yourself a nice cuppa and a little snack whilst you wait, it will be fine.

Regards Alan

YES! IT WILL DELETE All YOUR MUSIC AND MOVIES!

When you "back up" and ipod/iphone all that is saved is things like calendar settings and your apps. Everything else is gone.

I know this because I just upgraded my own ipod yesterday and am still in the process of restoring it.

Luckily I found a FREE program(SharePod) that will back up your entire iphone for real- totally free. Plug in your ipod, (close itunes) then open SharePod. It will display a list of your data complete with their proper titles and artists (most of the free ones rip with crazy file names).

If your computer has the space (and I highly recommend this) you can copy all your stuff back to your itunes library and recheck "sync this ipod with this computer" after the upgrade.

If, like me, you do not have the free space, you must save to an external hard drive and manually drag it all back after the upgrade. It takes longer and is more messy, but it all works out in the end. Just make sure you select "complete backup." http://www.getsharepod.com/