I am a little confused why you are choosing 2015 instead of 2014. My reasoning is this:
2014 - First full year for PS3/XB360 after their successor released.
2021 - First full year for PS4/XB1 after their successor released.
Am I missing something?
curl-6 bet me that PS5 + X|S sales would reach 56m before year end 2023 and he was right.
My Bet With curl-6
My Threads:
Master Thread, Game of the Year/Decade
Switch Will Be #1 All Time
Zelda Will Outsell Mario (Achieved)
How Much Will MH Rise sell?
My Bet With Metallox