Pretty well all the blueblood programs were very much opposed to this rule change. For one, they really do not want to see the NCAA get any older than it already is. In today's D-1 hockey, true 18 year old freshman are rare, comprising less than 8% of all incoming freshman. Even 19 year old players are only about a quarter of all recruits. The bulk of players entering college hockey are 20 and 21 year old. This change will pretty well much solidify this trend.
I don't think many here understand the power that agents (or "advisors in NCAA speak) have. These agents weigh really heavy of the decisions that young players make. The advice for most high end prospects will be to sign an ELC as soon as possible. The very best players in the NCAA are at usually two and done. A lot of these players will, in the coming years, choose to play in the CHL and the advise most will be given is to sign early, go to development camp, progress to the main camp and then back to the CHL (or if what I am hearing comes to pass, split the year between the AHL and CHL) all the while collecting your signing bonus and earning a pay check if you stick at the pro level.
As for NIL, the deals most schools offer do not compare to the amount made from signing an ELC and the NCAA-House settlement will rein in the pay to play side of these massive NIL deals you are recently seeing. So, a school like B.C. will find it much harder now to offer a players like Leonard a 25k year NIL deal for well not really doing much in the way of selling your name, likeness and image. All NIL deals above 600 dollars will be scrutinized by 3rd party arbitrators to see if they are legitimate. Now of course that doesn't mean that an up and coming generational talent wouldn't command a lot of money, his deals would just have to be legit.
We are only talking about high first round picks here, the rest, especially those drafted in say the 3rd/4th round or less will be steered towards the NCAA for a longer development time. Now of course some high end players will continue to choose the NCAA route after two years in the CHL, especially American born ones but there may be fewer of them. In the end the number of drafted prospects in the NCAA will really increase as will the number of NCAA NHL alums.