Why the hell would you do that?
That "May" is what will cause people to try it and find out the hard way.
You're not the one who had to disable their PM's because of being bombarded by people who did that last OTA and then were stuck not being able to root.
All because they couldn't wait 1 day to load the rooted version. Fortunately for them, OTA 1.47 was cracked, but that doesn't mean the next one will be. If I'm not mistaken, it took over 2 months to root the Incredible. Most people haven't even had the EVO 2 months yet. So, when the Froyo OTA unroots your phone, you could be stuck for over 2 months.
Yes, there is a good chance that it will be cracked, but the fact remains that it's better to wait for the rooted version than to just do the OTA and assume that eventually there will be a work around.
And yes, there is a very small chance that it will not affect the rooting process at all, but, if you're hoping for that, then you're probably also hoping for Android 3.0 this September.