Two points (and I don't think there is much speculation in that):
A long-stay visa or residence permit from a Schengen country exempts the holder from any visa requirement in the Schengen area. That's a very generic provision covering all such visas and actually necessary for the Schengen area to function so I don't this changing even if the US were to be added to the list of countries whose citizens require a visa to enter the Schengen area (OTOH the complete collapse of the Schengen area is a very real possibility IMO). The same is mostly the case for Bulgaria, Croatia, Cyprus, and Romania, while the UK and Ireland have other rules.
Restrictions on US citizens are not forthcoming. For multiple reasons, the EU Parliament is loudest but it has no real power in the matter. Member states whose citizens require a visa for the US (first and foremost Poland, which is in the Schengen area, but also Bulgaria, Croatia, Cyprus, and Romania) are understandably unhappy and would like the EU do something. The Commission also seems keen on pushing further based on (not unreasonable) principles of reciprocity and, presumably, because it's anxious to be seen helping all Europeans instead of caring only about the interests of the bigger, richer countries.
But none of this matters all that much because before anything happens the Council has to agree. That means that the governments of most countries (and especially the larger ones) need to agree and, until now, countries whose citizens already enjoy eligibility for the US visa waiver program have been very reluctant to risk putting that in jeopardy to make a point on behalf of the handful of countries who don't. Consequently, every few months, they try to find some way to step up the pressure through some form of official complaint, a deadline, a new report, etc. without ever actually doing anything drastic. This non-binding resolution you have been hearing about is one example of this but this has been going on for years (literally).