In the past 10 years, by my unofficial count culled from Wikipedia and other sources, there have been five players who were offered offer sheets (or is it offered sheets?).
Ryan Kesler....offered by Philly....matched by Vancouver
Thomas Vanek...offered by Edmonton...matched by Buffalo
Dustin Penner...offered by Edmonton...accepted for the full compensation
David Backes...offered by Vanouver...matched by St. Louis
Steve Bernier...offered by St. Louis...matched by Vancouver
So, only once in five ten-plus years has a team lost an RFA. Keeping these odds in mind, be it because of GM collusion, GM's believing it's a bad deal...whatever...the historical odds point to offer sheets not being given. And though you obviously want to attack the champion and the Hawks are in a precarious situation with the cap and have little bargaining power, Stan Bowman isn't exactly reviled around the league as someone other GM's want to attack. At least I don't think so.
Now, signing RFA's was slightly more in vogue in the 90's than the last decade, but even still, that Wikipedia entry (which yes, can be taken with a grain of salt the further you go back), only has 24 signings, the bulk of which were in the early 90's. And how many CBA's ago was that?
So, even though we should be mildly concerned about other teams trying to poach our RFA's...and let's be honest, when we say that, we're basically talking about Hjalmarsson and Niemi, I think recent history shows that we don't need to be too worried. Particularly with Niemi, with the load of unrestricted free agent goalies who are more established (Cup win notwithstanding) who are out there.