Android 2.2 for HTC Evo 4G has arrived. Users have started receiving the OTA update notifications. The firmware version for the OTA is 3.26.651.6 and clocks in at 84.34MB.
As the update will be rolled out gradually, do not worry, you will also get it very soon.
And This Android 2.2 update will not wipe your personal data (contacts, apps, settings, photos, etc.). That said, it is always prudent to back up your device before any major software update. There are many backup utilities available in Android Market.