According to Stefen Rosner, a local Islanders reporter, Lou Lamoriello and the Islanders are circling around the option of an offer sheet if Rasmus Sandin would consider signing one.
If the above signing numbers are accurate that would give the Islanders around $3M in cap space to offer sheet Sandin. However, looking at the Islanders' depth chart, Sandin would once again be the seventh defenseman as they already have Adam Pelech, Sebastian Aho, and Alexander Romanov on the left side.
Now there is more of an opportunity with the Islanders to secure a spot in the top 6, but would Sandin want to go from the Center of the Hockey Universe to Long Island? Maybe, but that would mean the Leafs aren't matching the proposed offersheet, which would be doubtful because they would get only a second round pick as compensation.
As of right now the Leafs have 9 NHL defensemen and are over the cap so a trade or two is likely to happen. Not to mention, teams are allowed to exceed the salary cap by 10% in the off-season. That means the Leafs will have no issue matching an Islanders' offersheet and figuring out the rest of the roster at a later date.