All Access Upgrade to Series X

What exactly is the benefit of the All Access "upgrade option"? Per the terms and conditions, I have to purchase a new 24 month subscription when i trade in my old console and the payments "may be higher".

Wouldn't it be better for me to just sell my old console on eBay then sign a new contract for the series x when it comes out?

Not really sure what's special about an "upgrade option" when anyone can just sell their old console and buy the new one. Doesn't everyone with an xbox effectively have the "option" to "upgrade"?

:)