There's a thread over on the other forum that requests the inclusion of this transition ...and the author of the 3rd party app (Virtue) that makes it currently possible to do this has freely offered to help Parallels people to put it Parallels Workstation as a self contained feature. So: it would be great to see a post from a Parallels guy over there to express an interest. EVERYONE who looks at that screen shot is wowed - put it on the packaging box for the product and sell a whole bunch more!
As long as it's optional. Last thing I want is some goofy animation slowing down something that should be instantaneous. But then I'm the guy who turns off all menu animations and rips out the 'Microsoft Agent' by the nerts under XP, and WISHES OS X let you turn all that crap OFF without installing a 3rd party app that just consumes more memory to do it.