"tempdb metadata memory-optimized" configuration option
As far as I can tell the feature has not been officially announced yet.

There are a couple of resources available on this feature from members of the community:

Youtube video from Erik Darling

Blog post from Ned Otter

This would appear to be the configuration option that will allow you to put some TempDB metadata tables into memory, preventing many types of resource wait and hopefully speeding use of that database up on busy systems. The value of the configuration option can be found with this query:

SELECT * FROM sys.configurations
WHERE configuration_id = 1589