Doughty is a lock for 2022. Anyone who thinks otherwise is totally out to lunch.
Rielly-Doughty
Chabot-Pietrangelo
Keith-Makar
You also bring 2-3 of Letang, Hamilton, Theodore, Ekblad, Morrissey, Parayko. Assuming Burns isn't up to the task in two years time.
Could swap out Keith depending on how he's skating in two years time, but if the wheels don't fall off, I think him and Doughty are both locks. Chabot, Makar, Rielly all have minimal big game experience with the former two I am projecting to improve and be staples on the blueline for Canada for years to come.