A series is always a toss up. I'm not going to toss insults just because the other team is a rival, so let's take the homer glasses off and be realistic.
Right now both goalies are putting up the same save percentage. We can ignore goals against because the teams have left them out to dry on several occasions. While I love Igor, I do feel his confidence gets broken a lot quicker. Rangers have been better at scoring 5 on 5 goals as of late, but if that dries up, well that's a big problem even if you're at the top in powerplay ranking.
Islanders are 3rd in the league for point percentage during the month of December. Top 5 during December in goals scored per game. So they're going in the right direction for sure. However, they probably want to find themselves in the lower half of the league when it comes to goals against, so you can't start sacrificing defense to score.
I hate to be a party pooper here and ruin the rivalry fanbase shots, but a 7 game series right now could go either way, and nobody should really call it an upset in either direction.