I was informed by NI support that the S3 I just bought is a Mk1, and that therefore I'm not eligible for the Traktor Pro 4 upgrade (I bought it 3 days before the announcement).
I've never heard of a Mk2 S3 (I've heard of the Mk3 S2 and S4 though)!
Pretty poor info available - especially as I would have asked about a Mk2 controller before buying.
Anyone shed some light please?