Go ahead and root it now, its easy enough to flash back to stock. Always flash to stock ed1 with Odin, then accept the latest OTA to get the latest basebands, then flash any package with a custom kernel, CWM, and a compatible ROM (or you can do this individually, just make sure they're Odin tarballs and not zips). That won't change no matter what updates there are, and flashing new kernels and roms is still gonna be the same. We may see a stable GB soon from Team Black Hat, or we may get an official release from Verizon, but either way its no problem. Anything that a dev does will include instructions about how you flash it and what you can flash it over, anything official is just flash back to stock and accept the OTA.
Keep in mind that if we get an official OTA of GB soon, you likely won't want to accept it right away, as it may include extra spyware like Moto's GB does restricting how you use the phone and data that you pay for, and it would likely be a week or two minimum before it was rooted or had any custom ROM's built from it. Something from a dev won't have those issues, but likely won't be stable right away, so either way you won't be flashing right when it comes out if this is your only phone.