The National Letter of Intent (NLI) was a formal, binding agreement between prospective athletes and college programs. The NLI will be replaced by a new financial aid agreement that will provide many of the same core functions as the NLI and will likely be tied to a contract related to an impending revenue-sharing model across college athletics. Per the NCAA, once a prospect has signed a written offer of athletic aid, other schools will be "prohibited from recruiting communications."
The early consensus is that this will not change much. With the NLI gone, players will sign financial aid agreements, scholarship agreements. This sets up better with the looming revenue-share, so there will be more of a contract with the players and schools. For 99% of players who are looking to be Division I athletes, there will be little change. However, there may be changes in the recruitment calendar as there does not seem to be any deadline that that paperwork is signed or signing period window.