There is pretty much zero chance this change results in any meaningful numbers of CHL players leaving for the NCAA in their D+1 or D+2 season anytime soon. NHL teams have significant influence on a players development in the CHL; they do not in the NCAA. And there is no indication that prospects are likely to go against the wishes of their drafted teams at greater frequency as a result of this change.
Something that many people do not appreciate on this site is that NHL will not be interested in their drafted prospects leaving for a system that they have no input in. While development in the NCAA is certainly better for some prospects, for example, American players more comfortable in the college system, NHL teams will be very reticent for their 1st and 2nd round picks from the CHL to leave for the NCAA. Not only does it increase the chance that the player will not report, but now that player has left their development ecosystem, will not sign an ELC, and will now play in a league that plays far fewer games with academic responsibilities on top.
The number of prospects for whom leaving the CHL for the NCAA in D+1 or D+2 will be the right development move and the right personality fit is going to be a very small number, and will likely consist primarily of later draft picks (3+ round), Americans, and prospects whom are playing for lower quality organizations with significant travel time. If the CHL-NHL agreement is amended as expected, allowing those players to play in the AHL earlier will likely be a preferred choice over having them not sign an ELC and leave for the NCAA.
As has already been the case, this change is primarily for CHL alumni, including overage players who are not playing on a playoff roster. It remains to be seen how many players who previously chose the BCHL/USHL/USHS will move to the CHL. Perhaps some of those players will sign agreements with their CHL team allowing them to leave after their draft season, but if they're players of Makar, Fantilli, or Celebrini's quality, that probably just means they play their draft seasons in the CHL and then move straight on to the NHL.