Augustin Piza.
His design focus on smaller footprints and more fun will be as, or more, important to the future of the game as any of the names previously mentioned. For purist aficionados, it will be apples and oranges and/or heresy, but if it helps address the unavoidable demographic shifting that lies ahead, Augie's creativity will be a shining example for the game evolution.
As the famous British statesman, Benjamin Disraeli once said: "Change is inevitable, Change is constant." IMO, less land, less water, more sustainability, more accessibility and less time will be the mantra of the next 50yrs of golf.