Here's an article about the bass
Justin Chancellor’s New Warwick Custom Shop Masterbuilt Bass
I haven't read anything about ditching Wal, but when you've essentially been playing the same Wal bass for almost 25 years and then suddenly have a custom Warwick built with custom pickups and do some promo videos with Warwick, one can't be blamed for assuming he's making a switch
Eh, don't buy it. Id be very surprised to see him on a stage with a Warwick. Maybe I'm wrong.