Microsoft is apparently fond of releasing multiple editions of the same OS with similar names (witness the multiple versions of Vista that just came out). So it's no surprise to see that Crossbow will be continuing that trend. Hopefully, though, these new names will be a little easier for folks to parse. "Professional for PPC-Smartphones, "Standard" for non-touchscreen-smartphones, and "Classic" (aka, why the heck aren't you using a smartphone?) for standard PDA-PPCs.
Crossbow, however, aims to fix this. Crossbow is Windows Mobile 6, and instead of the confusing naming scheme above, Microsoft has apparently decided to change to a more familiar sounding format.