is the new...

(something) is the new (something)

Something has replaced something else as the most fashionable, trendy thing of the moment. In the office of this young billionaire, jeans and a T-shirt are the new business casual. Trust me, navy is the new black when it comes to winter jackets.
See also: new
Farlex Dictionary of Idioms.

... is the new ...

(British English, informal) used to say that something has become very fashionable and can be thought of as replacing something else: Brown is the new black. Comedy is the new rock and roll. Fifty is the new forty.
Farlex Partner Idioms Dictionary
See also:
  • (something) is the new (something)
  • a thing of the past
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a straw will show which way the wind blows
  • a crack at (someone or something)
  • all right
  • (you) wanna make something of it?
  • all for the best
  • a slew of (something)