The streaming aspect of this deal is little changed from the current deal. A relative few out of market games. ESPN is taking over the marketing of what is now called nhl.tv, which is a separate thing.
In the linear space, which is what really matters, ESPN bought about half of the package now seen on NBC and NBCSN. Someone else will buy the other half. You local team will remain on your local RSN. The amount of hockey on linear TV will remain the same as today, just spread out between ESPN linear and someone else linear.
The big news is that, for better or worse, ESPN linear is going to carry the NHL, which means ESPN's talking heads will cease to ignore the NHL. Of course talking about the NHL requires thought and knowledge, and it continues to be much easier to call for somebody to "get paid" and argue about who "is the man" and other such NBA nonsense.