Comment by mmmBacon
P4 has more or less gone nowhere. Tofino was a full generation behind and didn’t make sense. P4 was compelling because people thought they’d solve the Elephant flow problem with traffic engineering in P4 but the resources to actually do this at scale never materialized for many reasons.
P4 as a language is still used on some programmable NICs for describing packet parsing dataplanes and exists as an HDL. Unfortunately the SDKs are not always exposed to small scale companies or universities like Intel did with Tofino.