The Encore Q400 fleet is modern (average age 4.3 years) and can use runways at regional airports that equivalent capacity jets can’t and fly short routes more efficiently - both aerodynamically and cost effectively.

With the current research from Airbus and other companies studying future short range aircraft (up to 1000km), electric propellor or hybrid turboprops with primary electric propulsion are probably the future, but not I would say for 10 years or more if I’m optimistic, 20 years if realistic. Jets are not particularly efficient unless they can spend most of their flight at optimum cruise altitudes above 11,000m / 36,000ft, which is not practical on short routes.