All we have at this writing [November 1, 2016] is a press release. As noted, this announcement comes 2 years after the tomahawk press release. Two years, 2X the ports, 2X switching bandwidth.

slide shows Tomahawk2 BCM56970 feature highlights

We are told that there is more stuff [buffers, forwarding tables]. We get to wait to find out how much more.

Here's a more substantial review. And here's another one.

OEMs that know the most about Broadcom ASICs and are willing to offer details are Cisco and Arista. Cisco has a graphic from 2018 that shows both the total buffer [42 MB] and that the four-slice segmented architecture from Tomahawk has be retained.

Architecture slide from CiscoLive shows buffers and segmentation