Russia is not the problem, some people are concerned about China, Indonesia, India, Vietnam, etc. So they want to keep the F-111 for long-range interdiction, because the Hornets and F-35 lack the range. There's an entire website dedicated to this argument:
http://www.ausairpower.net/I think Australia made a good decision though, investing on Hornet upgrade, stand-off cruise missiles, tankers, AEW, and lease Super Hornet to fill the gap until F-35 enters service. Okay, so maybe they are Super Bugs, but for Australia it is the best option availabe to fill the gap, and I am glad they did recognize and fill the gap!
Of course the F-22 would be ideal, but it's not really an option for Australia (yet...), neither is buying Flankers (Su-34 would make a good replacement though, too bad it isn't made in the US of A).
The F-111s are old, dated, expensive to maintain and operate. It's time to move on and get over it.