Android Central is reporting, based on an internal memo leak, that the Thunderbolt should receive a fix for the reboot issues in the second half of June. Until then, most users will just have to wait it out (unless you've rooted and gone with a custom ROM/radio).
One has to wonder how this will affect the Gingerbread update that we were also supposed to receive by the end of June. Unless it's packaged altogether, which does not appear likely based on the memo, I would guess a delay is unfortunately imminent.
Source: Thunderboltforums.com via AndroidCentral