If they did it would be for the 2018 season as the current TNF deal goes through the 2017 season.
TNF is a gong show. No ratings, no proper rest or preparation for players, and no appeal to many.
...I'd love if they scrap TNF and rather have a Saturday night football instead. More time for teams to do all the things they are limited to doing on TNF, and it's a lot more reasonable and still allows the NFL to have a game scheduled outside of Sunday and Monday.
If I remember correctly there were a couple games scheduled on Saturday a few seasons back, I think in 2015. From what I remember, everyone loved it and people generally enjoyed having some football to watch on Saturday. The NFL also has Saturday games when it's wildcard playoffs anyways and it's always a success. I think Saturday would be the most reasonable day to change to.