If you do nothing and install the new version it will wipe out the old version. The safest way on Mac anyway and I have 3 hard drives , is to copy the old version, move it to another drive, and for good measure rename it. I tried moving a copy from applications to the desktop and that got deleted, perhaps if I had renamed that it would have been alright. You can experiment a bit to find out what works but save a copy either on another drive and back it up on CD for good measure. I made sure I did, in my brief sojourn as a beta tester .... I hope poor old Deacon got his asprins after.

I'm stubbornly sticking to 4.8.1 until I hear the rave reviews....