I do agree that Amex most probably favours their house brand cards vs the Co-brands as they don't have to buy the points/rewards from other partners.
There were some rumblings on FT that a friend of a friend who works at Amex said Plats would get * Gold, it's really all speculation at this point.
Amex could very well come out with a $299 card that offers similar benefits to the $399 TD card.
We should start a betting pool, everyone picks an AF, Bonus Points amount and benefit.