In theory this should be 100% fine.
There has been no major change in how iTunes & RB link up between V5 & V6. Working well for me, other than I'm having a minor bug with 6.0 not liking dragging and dropping playlist folders.
My bug FYI is that overwriting playlists within existing folders is not working how it should, however - individual playlists, and dragging and dropping new folders of playlists is absolutely fine.
Give it a test run!