I got up this morning and watched the first four sets (although I knew the outcome before I began watching). Wawrinka (age 31) is a beast, but this tournament is destined to be The Final Showdown between The Legends: Federer (age 35) - Nadal (age 30) in the Men's Singles final; The Williams Sisters (ages 35 and 36) in the Women's Singles Final, and The Bryan Brothers (age 38) in the Men's Doubles Final.
Something similar to this happened in the early aughts with Sampras (age 31) winning the U.S. Open in 2002, and Agassi (age 33) winning the Australian Open in 2003 - neither were "supposed" to win any more majors.
Enjoy this - it will almost surely be the last time you ever see this group of players in a final round.