What makes you so confident the FCC couldn't win in court? My understanding is that states have some right to additionally regulate, but only to the extent that federal law allows it.
Sorry if my take is a little confusing, here is some more coverage: [2], [3].
[1] http://www.opn.ca6.uscourts.gov/opinions.pdf/16a0189p-06.pdf
[2] https://www.forbes.com/sites/danielfisher/2016/08/10/fcc-los...
[3] https://arstechnica.com/tech-policy/2016/08/in-blow-to-muni-...
A law banning NN will never get passed due to gridlock (thankfully), so barring some huge change in public opinion I don't see states being prohibited from enforcing NN.