I'm holding onto a theory that the Millennium trains are going to have a full overhaul soon(ish) that will include a complete interior and exterior refresh, complete with Waratah-style logos (ie orange at the front, large logos along the sides). Considering how similar they look to a Waratah (for passengers, not enthusiasts), it seems a good bet.

Between you, me and the fencepost, they're due. There seem to be a few out of service with "issues" (there's at least one K set and one T set on Sector 2 services doing Millennium runs), and the seat fabrics have a long-term grime issue in which they're past the point of cleaning... I'd wager on them being turned into pseudo-Waratahs, myself.

All speculation on the part of me, Raichase, so assume the opposite to be true.

Which it is! Saw an M Set yesterday with the regular (small) Sydney Trains branding (ala S Sets). M21 if I recall correctly.

Also saw a Tangara (sector 1) with the small Sydney Trains branding for the first time on Monday.

there's at least one K set and one T set on Sector 2 services doing Millennium runs

In anticipation of many K Sets having sector 2 as their new home, there will be 4 sector 2 K Set runs starting in just under 2 weeks.