Appeared in the trade press on Nov 3, 2015.
Digging into the data sheet, the power supplies in the 2RU model are 2X the size of the 1 RU model. The suggests that there is more going on here than just powering QSFPs. There is likely more than one Tomahawk in the box to support the port count. That the data sheet says packet memory is the same for both models is either a mistake or a reflection that memory is segmented to reduce its effective size.
Duffy and NetworkWorld say that the switch comes with an ONIE boot loader and is available without JunOS. Interesting.