ThatsBoBo - 5:12 pm on Feb 21, 2012 (gmt 0)
No, you will not need to replace any Adsense code for high end devices.
If you want to continue using Adsense for Mobile for older devices such as the older Blackberries, you will need to replace that code before the deadline.
On my sites with no adsense for mobile, ads are showing just fine, but with those god awful arrows. :)