Your game one lineup doesn't have to be your game 83 lineup.
Finding bottom pairing defenseman at the deadline is a lot easier than trying to make a trade to improve the top of your lineup but not having the cap space to do so because you're overpaying for depth players.
I do think Mayfield is good and would be interested in re-signing him if I was the GM of the New York Islanders (which I'm not but should be), but there are also scenarios where I can see it not coming to fruition as well.
Also, there's no harm in discussing who would be the internal options if Mayfield departed The Island next summer, especially at this (boring) juncture of the offseason, and honestly we should all want Hutton to be a potential solution...NYI got him for free and he's locked up for three years on the cheap. This is how you develop cap flexibility to improve the top of your lineup, it's what everyone is clamoring for and it's what a team like Tampa has been able to do for years.