Pedrovigdny,
Why are the downstream system users "off limit" as you claim?
The SCOTUS did not rule that a patent holder can't opt to go after the downstream manufacturers instead of the original chip manufacturer. They simply ruled that, once you license the original device manufacturer, you can't go after their downstream customers.
That being the case, TPL can choose to forgo chasing after the remaining chip manufacturers (i.e, those who haven't licensed the MMP yet), and instead go after their customers.
I read somewhere that INTEL & AMD together account for only about 20% of the global chip market, so there is plenty of potential infringers to go after.
Knixx