I am about to do the same thing and would rather not for an update. akazabam, can you lend some knowledge on how to do the OTA without un-rooting?
Thanks....
Sure. Assuming you have full root, you need to install a ROM based on 3.70. Some people choose to take the opportunity to try out some custom ROMs, while others just want to stick with something as stock as possible. Here's a couple of very close to stock ROMs:
[ROM] RUU SuperSonic EvO 3.70.651.1 OTA - Stock - Sense - Deodexed & Odexed Version - xda-developers
♠♠♠[SteelROM RevI.2]♠♠♠ UPDATED 12/24 v3.70.651.1 │Rooted│ DeOdexed - xda-developers
I won't go into detail here, but deodexed simply means you can apply themes (such as those found on xda). If you want to try any custom ROM, you can find a full list here:
HTC Supersonic/ROMs - XDA-Developers
Just make sure you use one that is based on 3.70.651.1. The list shows which ones are.
Anyway, once you flash your ROM of choice from recovery, you will need to update your radios, etc. to the latest versions. You can find them here:
[ Radios ][ 12-17 ] All EVO Radio, WiMAX, PRI, NV & HBoot versions - xda-developers
You flash them from recovery like any other update package. Make sure you follow the prompts when doing so. It looks a little different when updating than other updates. That being said, you can either update them all at once with the combo update or separately. Should you run into any issues, previous versions of the radios are provided. I strongly suggest you record your current radio versions somewhere so you know what to go back to. More than likely, you have the version directly before the latest, but only you know what OTA you accepted last.
EDIT: And just so no one thinks this is off topic from the OP, this is valuable information. rlister39, keep this in mind before unrooting to accept an OTA. You lucked out this time since unrevoked got an update, but many, many people unrooted before unrevoked got the update, and were stuck without root.
EDIT2: rlister39, I totally missed where you asked if you could update after unrooting before you actually did. So sorry. Anyway, you can reroot again, now, if you like. Just follow the above instructions should there be another OTA.