If I read correctly, the Silo piezo is discontinued but the Silo Special did not loose that option. Also FWIW I tried to order a Silo Special with piezo from Sweet Water with SB finish and roasted neck and they said yes to everything I wanted except the finish which that list confirms the SB finish is discontinued. So I'd say ask your dealer but I think it's available on the special.
Piezo is still available on the GameChanger Reflex in addition to the JP & Majesty lines (note that the piezo is not available on the JP16 with Floyd style tremolo)
My understanding was that piezo is gone on everything except what Pete said. The only options available on Silhouette Special at music-man.com are colour (black or white), maple or rosewood board, matching headstock or not. Piezo not listed at all.
There are still some Axis HH models with the piezo available for purchase new. The tremolo bridge version is more plentiful than hardtail with the retailers I looked at. Not the same vibe as the Silo, but if the piezo is crucial for you, it's an option.
Yes, there will still be some stock out there for a while as the change only happened less than a year ago. But new orders for the option won't be accepted by EBMM.