The Islanders have been trying to re-sign their veterean defenseman, but according to Arthur Staple of Newsday, Streit turned down the team's most recent offer. That leaves one option.
Streit is up there in age (he'll turn 36 in December), but it's still a significant loss for the Islanders. In addition to being their captain, he was also a key cog on their blue line, playing more than 23 minutes per game this season. He isn't the greatest defenseman in his own zone, but he still puts up offensive numbers, scoring six goals to go with 21 assists this season.
It will be interesting to see what kind of demand there will be for Streit. Teams don't usually crawl over one another to sign players that old, but Streit does still have some gas in the tank.
If the Islanders' captain indeed leaves, you can expect with utmost certainty John Tavares will be given the honor at some point. It seems inevitable as he is already an alternate captain and is the face of the franchise.