Well, Rosebank is not the first of the Flora & Fauna Serie to be discontinued and it certainly isn't going to be the last one either. Aultmore, Balmenach, Brackla, Caol Ila, Clynelish, Craigellachie and Speyburn are other discontinued ones that are becoming harder to find.
However it's still easy to find bottlings of the Rosebank F&F at several online dealers. I read somewhere that Diageo had loads of bottled F&F Rosebank (just don't remeber where) so I don't think you need to worry about getting a few bottles. The same is valid for Pittyvaich which was bulldozed back in 2002.
Rosebank 12y. F&F is a wonderful whisky so try and get it while you can. However, it would also be nice to see a new expression on the market.