First, the proposal is 17 regular season games with three preseason games. It allows for teams to play in different areas of the US that don't have teams (like LA) or internationally without losing a home game.
Second, odds are very good that the NFL moves to this schedule next season. Potentially the next.
Third, the NFL doesn't need four preseason games. I bet most head caoches would say 4 games are too much. The 4tht preseason game is a waste now. There is no evaluation going on because rosters are already pretty much set and the only objective of these game as to avoid injuries. Any player who hadn't impressed coaches enough to make the roster in the first three games, isn't going to change that in the fourth. Coaches could easily make their evaluations in 2-3 preseason games.
When the league switched from 6 preseason games to 4, people made similiar arguments about the evaluation process and nothing has really changed. Coaches see these guys in practice and scrimages all the time. Only a handful of players really need be evaluated in real game conditions. If you have a team that has more than 5-10 players on the bubble, you might as well continue your evaluation process into the regular season because you ain't going anywhere. Most teams have top 40-45 roster spots or more already locked in before they even open camp.
Personally, I like the proposed change to the schedule. As a season ticket holder who has had to pay full price to go to a fourth preseason game where Belichick has already had the roster basically locked and him mostly play players who are going to get cut just so he doesn't injure players who are going to make the roster, I fully support a 17 game season with a 3 game preseason. I think it is a perfectly good system.