DM 5 is compatibe not only with Tour, but also with most previous models, including, Storm, Bold, Curve, etc.
The only major difference with DM 4.7 or4.6 is that sync is much much faster. Even with gigantic Contact lists and Calendars it takes a fraction of the time to sync than wehn using 4.x DM versions. I have been running DM 5.0.0.8 since it leaked over a month ago and it works very well indeed!
You DO NOT need 5.x OS running in your device, any 4.5 or latter OS version works fine!