The large majority of NCAA programs are going to want 20 and 21 YO players because that is the type of players they are recruiting now. The real battles are going to be between the Michgians and B.U.s and the various CHL clubs vying for the really elite talent. As mentioned, the CHL will encourage many of those players to sign ELC's but they will also want to give them ample ice time by running the PP and on the PK. and making the CHL older may hamper that ice time availability.
I don't think that a few extra 20YO's on each roster would take away time from elite 16YO's; the guys who would be affected, either through less ice time or having to wait another year to land on a roster, aren't going to be fast-tracked to higher levels anyway. A lot of them would become those 20YO CHLers who could use the extra year of development before moving up. And anything that improves the overall calibre of play might help to encourage a few guys who are considering moving to D1 to stay in CHL.
There's going to be an adjustment throughout the junior levels with this change. D1 is going to get stronger and it's going to get older in terms of its median entry age, especially for the mid-tier and lower-tier recruits. Probably AHL standards of entry will increase a bit. I think CHL should accept the new reality and adapt to take advantage of the situation rather than just holding to old ways.