I really think a true All-Star season could revive the series, it would be a good way to go for season 30. I know CBS loves to say no older teams but I really think classic teams like Charla & Mirna and Dustin & Kandace could draw some viewers in (yes, I know they've raced twice already but if some of the teams we've had can race three teams, these two teams more than deserve that opportunity).
Colin & Christie would be amazing to see race again, or what about Flo & Zach or Tara & Wil? Even though some of these teams may not have been previously interested, they may be now after all of these years.
Amazing Race was at its height of popularity when we had the classic moment of Lena & Kristy never finding their clue in the hay bales, that's something even casual fans will remember, they deserve to race again and really should have been on Unfinished Business. And although some people aren't fans, even another Rob & Amber run would surely catch some eyes.
These are just a few examples of course, but we have some amazing classic teams that if CBS would actually do another real All-Star season, I believe we could get a lot of viewers to tune in.