You will lose it all, but it should be a one off loss.
View scheme's you'll realise why you've lost your old ones as soon as you install v9.1
It's a totally different feel and way of browsing, once I got used to it, I dropped all my old schemes and built new ones.
The new ones dont particularly work that well with v9.1
U'll find urself creating a lot of double columns with v9.1 and making the first one grouped so u can navigate around the second one a lot faster
ie: Artist (Grouped 3)/Artist
gives u
A-C
D-F
G-I
etc
so u then click on that for ur first one to filter down the second.
Also, as you no longer have tree's - u can start browsing from anywhere u want along the scheme so if u do this:
Year/artist/album
U can ignore year if u want and just do artist
or ignore them both and go straight to album
Before you HAD to use the first items in a view scheme - now u can just ignore them
It's a BIG change but definitely worth it - v9.1 is a LOT better than v9.