Very reasonable.
Furusawa may be speaking like that exactly because he's' retiring at the end of this season, so he's free to speak his own mind. It may be a kind of suggestion for the rest of Yamaha management, maybe trying to influence them. I have a feeling Jarvis would rather keep Jorge.
However, Jorge beating Rossi this year would be less decisive than it seems.
Stoner "decisively" beat Rossi in 2007, but that was not the end of Rossi. Whatever Lorenzo could do this year, it would hardly be the end of the story (unless Rossi retires). Nobody can rule out that Lorenzo beats Rossi (and Stoner) in 2010, but it can't be ruled out either, in that case, that Rossi comes back and wins in 2011. And/or 2012. One cannot be sure that Lorenzo will be capable to beat Stoner in the next 3/4 seasons either. Nobody has a crystal ball... And Rossi remains a very solid choice for another 3-4 years.
FIAT is there because of Rossi, of course, and would follow Rossi -- they wouldn't stay with a Rossi-less Yamaha.