That's probably so Micros can upgrade the db ahead of time in their office. I've done a few in-place upgrades and they're a pain. You can't upgrade directly from 4.7 to 5.2. You have to go 4.7 => 4.11 => 5.0 => 5.2 prerequisit => 5.2MR1a . The upgrade process consists of backup up the DB, rebuilding it, running the conversion, and backing it up again. Doing this with a database full of totals can take take a long time depending on it's size and the speed of the server. One of my databases is about 1.2G and each version upgrade took about 4 hours. I've also run into a few databases that tanked so badly going form 4.11 to 5.0 that the encryption got corrupted and the server had to be re-imaged. Part of the process also includes rerunning CAL on all the workstations, which can't be done until the server upgrade is completed. Depending on how many you have, this could add another hour or so to the total upgrade time.
When I started my upgrade rollout I put all of our restaurants onto Res4.11 as a first step. They're all running that way while I'm working on the 5.2 upgrades. Before upgrading to Res5 I test the 4.11 => 5.0 conversion for the database on a test server in my office to see if there are any problems. Micros could probably do this for you as well, but it takes longer so the upgrade will cost more.
There's another option if you're replacing your server and not upgrading the OS on your existing. Change the IP/Name on the Res4 server, disable CAL, keep it on your network and access it through remote desktop. That way Micros will be able to blow out your totals and give you a nice clean upgrade, and you'll still have your historical totals.