Shaw has never done anything too mainstream. I mean, everything is always a little different. I mean, yes they have done Cabaret, and Sweeney Todd, but nothing like The Sound of Music or Fiddler on the Roof. To me, the Shaw Festival has always been more adventurous in its seasons that Stratford. Stratford has always seemed more family, and "common" for some things, but have recently started to commission more work for themselves that isn't as conventional as you think. I also think George Bernard Shaw is more of an acquired taste than Shakespeare, and Shakespeare's stories are more widely known.
I think that they are like Encores in that they are trying to present shows that are great for many reasons, but a full blown commercial open ended run wouldn't be the best bet. I have always enjoyed their shows. The one I regret missing was a revisal of Mack and Mabel which was over seen by Michael Stewart's sister, and was acclaimed by Jerry Herman.
I feel like it is purely a coincidence, but at the same time seeing what other companies are doing with shows that could use a another look.
I would love to see more strange musicals from Shaw like "Dear World", "Kiss of the Spider Woman", "Allegro", or even "Follies". I am definitely going to see Brigadoon (because when we we see that again), and the Glass Menagerie. Stratford's musicals this year aren't exciting me too much.