Have Boeing's plant at Winnipeg become a lot bigger - maybe they build some 737s or something.
Have wheat and potash prices hit new peaks and stay there.
Have a cheap method for upgrading heavy oil be developed by e.g. the UofS and retool e.g. Saskatoon's former refinery to dealing with heavy oil. Then when you get bottlenecks (e.g. the current Keystone XL fiasco, but earlier), this refinery upgrades again to deal with Tar Sands bitumen. (It's a lot easier to move and export refined products, or even light crude than it is the bitumen product.)
Have SaskTel's early venture into fiber optics make Saskatchewan the world leading producer of fiber cable.
Have Saskatchewan's early lead in nuclear medicine (first calibrated cobalt bomb, betatrons, etc.), coupled with government funding for health care lead to medical tourism to Saskatchewan. So, instead (or in addition to) rich Americans and Arab sheiks flying to Rochester MN to the Mayo clinic, they fly to the RUH (which gets the 'Royal' sooner) in Saskatoon.
Have Morris Rodweeder in Yorkton expand, and get some more agricultural equipment manufacturing in the West (e.g. Massey-Harris/Ferguson)
Have Quebec separate, and all the Francophones who want to stay Canadian move to St. Boniface....
Have SED systems get a major NASA contract, or two, and use that as the basis for space electronics etc.