Of course they announce it today - I finally upgraded my iPhone X to a 13 Pro Max over the weekend :)
I upgraded through AT&T, who gave me a $700 trade-in on my iPhone X. I also snagged an additional discount on my new iPhone 13 Pro Max because I was OK with an unpopular color ("bamboo"), so my total cost ended up being around $200.
Apple's offering $150 for an iPhone X, and $430 for an iPhone 12 Pro.