nope
The Intel XMM7360 doesn't support either technology. The X12 doesn't out of the box, but it can with upgrades. To support 256 QAM, Apple would need a software upgrade to the base X12 modem. To support 4x4 MIMO, Apple would actually need to include extra physical antennas.
So that means while the iPhone 7 will be the fastest iPhone ever, it still may not achieve the network speeds that the
Galaxy S7$669.99 at T-Mobile,
S7 Edge, and
Note 7 do, as those have the new technologies.