Funny thing is, I know someone who did get to fly USAF C-17s. Not exactly in the capacity sm13464 is describing, but it happened. Regardless, I'm curious what the definition of "coming close to the end of my sea tour" is in terms of months from PRD. Did you come up with this idea yourself, or is it in the rumor mill? Kind of like that mythical C-12 gig in the PI.
But to answer the question, no, I have never heard of someone (1) from the USN and (2) with no C-17 background getting assigned an exchange billet with a C-17 unit. While you do have jet guys doing that type of exchange (i.e. pointy nose to pointy nose), I have yet to hear of any USAF types doing a 3 year tour with a fleet squadron in any other community (helo guys? anything?).