I spoke too soon.  Here's what FIRST has said:

SPIKE Prime will be approved for use in FIRST® LEGO® League starting in August 2019, and will participate alongside Mindstorms EV3, NXT, and RCX.  

Steve Scherr
Virginia-DC FLL Referee Advisor

On Thu, Apr 4, 2019 at 1:13 PM VA-DC FLL Referee Advisor <[log in to unmask]> wrote:
Because shipping is not until August, my guess is that the Spike Hub won’t be permitted as a controller. Probably everything else, though. 

We may hear something more at World Festival in a few weeks. 


Steve Scherr
Virginia-DC FLL Referee Advisor


---- On Thu, 04 Apr 2019 11:46:41 -0400 Skip Morrow<[log in to unmask]> wrote ----

https://education.lego.com/en-us/products/lego-education-spike-prime-set/45678

Lego announced the Spike Prime a few days ago, and I am seeing rumors that it may be acceptable for FLL:
http://fll.memphisfirstteams.org/2019/04/02/this-just-in/

Will Spike Prime be permitted for VA-DC?

Skip Morrow
To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list".
VADCFLL administrative announcements are sent via VADCFLL-ANNOUNCEMENTS-L. Visit https://listserv.jmu.edu/archives/vadcfll-announcements-l.html to subscribe.