"With all the New head coaches being announced for some top D1 schools, what does it mean for the recruits that have already committed?"
In one way or another, the new HC will remake the program with his own recruits. Now, this means that some of the former recruits become the new coaches recruits, while others will be formally let go or forced out. Verbals will be treated with the worth of a verbal,(I.e., worthless until the NLI); kids who signed NLIs will either become the new coaches recruits or be cut. See, e.g., Nevada , UA, and ASU.
Sometimes, what appears to be a disaster to a kid, will actually be the new coach trying to keep the kid's eligibility intact. For example, new HC tells the incoming recruiting class - before school starts - that the kid will be cut during fall or not make the spring squad. The NLI offer is good (kid gets the economic benefit) for the year (or more if applicable), but the kid burns a year of eligibility and may even need to sit out a year at a new school. By cutting the kid before school begins, the kid doesn't lose eligibility and can find another place. (Often the kid and family, can't see the benefit of that result, but it is better than losing a year.)
This is one of the unfortunate circumstances and the kid has no control whatsoever. If the NLI is signed, the kid is bound to the school; however, if the offer hasn't ripened into an NLI, the kid can reopen recruiting (decommit) and other programs wouldn't think twice about recruiting a worthy player for that program.