While the General Manager is the one who signs and trades players, most head coaches also have a heavy influence on decisions. That was especially true with Tom Thibodeau during his five years with the organization. Now that he is gone, it could signal the end of Landry Shamet's tenure with the club, as Thibodeau was the driving force behind signing him and giving him a role last year.
It is difficult to say anything definitive before the Knicks make a coaching hire (whenever that eventually happens). For all we know, Mike Brown, or whoever it ends up being, could be the biggest Shamet fan east of the Mississippi.
However, it is more realistic that whoever the next coach is won't share the same level of value that Thibodeau did, instead looking to other veteran guards on the market who could step in to fill his role.
Shamet provided value
This isn't to say that Shamet didn't provide value during his stint with New York. Thibodeau specifically valued the fact that he had played with both Mikal Bridges and Cameron Payne during their time with the Phoenix Suns. He was also arguably the team's best movement 3-point shooter.
He earned a spot in the rotation during the Eastern Conference Finals, and Thibodeauclearly had a lot of respect for how Shamet had navigated an injury that sidelined him for roughly the first half of the regular season. Part of that respect led to Thibodeau giving Shamet every opportunity to earn rotation minutes, something Shamet did towards the end of the season with his fantastic shooting.
The Knicks originally signed Shamet before the season was underway, before he suffered a dislocated shoulder in a preseason game, which led to the Knicks waiving him. The Knicks eventually signed Shamet back in late December after a stint with their G-League team, the Westchester Knicks.
The Old Guard
The next head coach will have decisions to make about multiple veteran guards on expiring contracts this offseason. Shamet will be joined in free agency by Payne and Delon Wright. The Knicks desperately need guard depth, so there is a chance one or more of those players end up back in New York, again, depending on which direction the Knicks go with their hire.
Payne played his way out of the rotation in the Eastern Conference Finals, while Shamet and Wright both saw their minutes increase in the team's last few games before elimination.