According to Pistol-Training.com there is
A formal proposal to remove all .40-cal guns from service and replace them with 9mm is sitting on the FBI Director’s desk and is expected to be approved.
A new ammo procurement would begin in 2015.
This would be an interesting revelation as .40 S&W was developed as a response to 1986 Miami shootout. FBI wanted better ballistics so 10mm was made, but after facing some problems, they went with .40 S&W. It influenced LE agencies across US.
There has been significant advances in ballistic science and now a 9mm JHP is vastly improved compared to those available in the 80s.
A few years ago there was the transition from SIGs to Glocks in .40S&W and now they are moving to 9mm, if the rumor is true.
From: Pistol-Training