Well, I am new in the BB community (1.5 years), and very new to the Mac (3 weeks), but I think your solution might be the free D/L from RIM called "PocketMAC." If you were to install this software on your Mac, and then copy all your many contacts from the 8700g into it (probably they'll go to "Address Book") then you could sync them back into the new Bold at some later time. I am not using my Mac with the BB, so I have not tried this, but "PocketMAC" may have a backup and restore function as does the BB desktop software. See the RIM page here:
BlackBerry - BlackBerry for Mac
I'm contemplating the switch from AT&T 8700c to Bold, and figured it was going to be pretty simple to just "restore" a backup or just sync with the new BB.
Let us all know how this works, OK?