The drastic changes to the NFL's replay system will have to wait another year, and probably longer. The Baltimore Ravens had proposed a large rule change in which only plays that were non-reviewable would be listed in the rule book. That change would have made many more plays reviewable compared to the current guidelines, the changes made instead were not so drastic.
The changes that the NFL did make to their replay system were to allow teams to replay the proper down, the spot of where a foul occurred, the status of the game clock, and penalty enforcement.
Don't get too excited about that last one, what they mean is that the way the refs decided a penalty was to be enforced can now be challenged. That does not mean you can challenge whether a foul was committed, the challenge would be if a team disagreed with the way the refs decided to enforce the penalty.
There were also changes made to streamline the rule book to be easier to understand, placing the non-reviewable plays before the reviewable plays in the rule book, and to include more things as non-reviewable along with removing the clock killing "spike" play from the non reviewable play list.
The things that became non reviewable are; whether a player had been blocked into a loose ball, the advancement by a player after a valid or invalid fair catch signal, the spot where an airborne ball crosses over the sidelines, and whether a player had created the impetus that carried the ball into an end zone.
The biggest change that was made actually began at the end of last year, where the NFL office is now able to be in direct contact with the official during the process of the replay. The NFL league office can now officially provide information to the official on how to correctly apply the playing rules. That includes information regarding the proper assessment of penalty yardage, proper down for the play, and the status of the game clock.
Overall, not a ton of stuff has changed to be honest. I actually liked the Ravens proposal of only stating what is explicitly not allowed to be challenged in order to give more plays, including unforeseen circumstances, the chance to be reviewed. Oh well, the NFL moves at a snail's pace so you get what changes you can get.
Here is the official rules with the changes that were made in red, special thanks to David Fucillo of Niners Nation for giving me the idea to add this.