Looks like new content has come out for PGA 2K21.
It's the Season One Clubhouse Pass. Seems to include the Detroit Golf Club and the Rocket Mortgage Classic. Plus a bunch of silly new gear and such, although Mizuno clubs seem to be added, too.
https://pgatour.2k.com/clubhouse/
However, to get the most out of this, you have to pay. There is a free tier, but you only get rewards after every fifth level up to level 75. Accessing all 75 levels of rewards is $8. For $15, you get all 75 levels of rewards, but also get to skip the first 20 levels and automatically unlock those rewards right away. And Season One lasts from today until 3/3/21.
EDIT: gdog is one of the folks who streamed content before launch, and he just posted this list of what's included in the update over on the TGCT forum:
Stuff in the paid season pass
• New Gear including:
o Mizuno Clubs Gear:
2 Drivers
2 Hybrids
2 Woods
3 Irons Sets
3 Putters
3 Pitch Wedge
9 Wedges
5 Mizuno Hats
1 Mizuno Glove
o Under Armour Gear:
9 Windjackets (male)
4 Button Polos (Female)
2 Zip Polos (Female)
o Goodr Gear:
4 Styles & 2 Colorways Sunglasses
2 Shirts (male/female)
Shorts (male)
Skirt (female)
Flamingo Putter
o Additional Gear:
Golden Outfit (male/female)
Cubert Outfit (male/female)
Stuff purchasable outside the season pass.
• Hockey Stick Putter
• Candy Cane Putter
• Elf Hat (unisex)
• Santa Hat (unisex)
• Elf Outfit (male/female)
• Holiday/Winter Sweaters (male/female)
• Holiday/Winter Toques (male/female)
Season Pass Premium is $15 has 75 levels.
You level up with VC so save your coins if you plan on levelling up.
He also confirmed that the Detroit Golf Club/Rocket Mortgage Classic is free as part of the update. It replaces event 22 in career mode. Is also playable in local/society play too.