Honestly, viewership will probably go down. Its not like flower power hippies are going to start watching football to make up for the right wing crackpots that are going to stop watching. However I do believe public opinion of the NFL will go up, and that it is getting easier for those in the center to join in the protest against trump's bigotry.
They did that last year, then came back for the divisional champtionships and super bowl. A lot of those people don't have much to look forward too besides football, they'll almost all crawl back eventually.