Will miners start excluding "spam" transactions once segwit is implemented? If so, why?[/b]
It's up to them.
As for Segwit, Segwit solves the old issue of tx mal. *and* also gives a capacity upg to those who want it.
Then why advertise it as a scaling solution, if scaling itself is a bad thing, due to not being instrumental to fee market developing?
Shouldn't they come up with some block-bloating code, to compensate for the nasty scaling side effect?