I think they've got it backward. 'Cloud computing' makes all desktop OS irrelevant. Which means it's easier than ever for me, working in a Debian ecosystem with Fluxbox/Emacs/Firefox as my main apps, to collaborate with peers using OSX or Windows, without them knowing or caring.

Besides which, whether Ubuntu is the top Linux distro is completely orthogonal to the capacity of Linux in general to serve as a desktop.