The FH6 and FH XP will be going away...
Basically, the FH7 is about 1/3 lighter than the FH6, is a better cold water reg, and should breathe a little better - although you may need a machine to really tell. Overall, I think it is just a much cooler looking reg...Jim Fox may have more points that I missed...I'll ask him.
And finally the feature I've wanted to see since the beginning... a new streamlined exhaust Tee!!