Matthews last season had one weakness, and it was in his transition game. He wasn't all that good at transporting the puck across the blue lines. Nylander excels at that, so he makes a perfect addition even with chemistry not taken into account. With Matthews growing in that area, I expect alternatives like Brown to look better beside him.
It's interesting with Nylander. He hasn't been a high percentage shooter so far. Obviously it will come up to some point, but I wonder if we overestimate the extent. I've been looking through clips of him in scoring chances, and I have a feeling that he is not actually a very good goalscorer. Terrific shooter, for sure, but he doesn't have that ability to understand the goaltender, or to disguise his shot, or use screens effectively. With him, it's mostly pitting his shot against the goaltenders stopping ability. He would probably do well to take some pointers from Matthews in that regard, or even with JVR.
Get Willy signed ASAP before he puts up ppg
When a player says that he doesn't want to look at an extension during the season, that usually comes true. I doubt we'll see anything happen until next summer, where I expect all three to get signed and announced at the same time.