Can we stop with the "he needs better endurance" thing? It may have been true when he was a rookie, maybe, but it certainly isn't now. Kakko is 9th on the team in ice time per shift at 51 seconds. That's the same as Trouba, and a whole 1 second behind Laf and Chytil, and 2 seconds behind Miller and Kreider. And keep in mind that Kreider is usually out there for an extended shift on the PP. If we looked at just 5 on 5, I'd bet that Kreider takes shorter shifts.
As far as speed, there are few players in the league who wouldn't be better if they were faster, but he doesn't NEED to get faster. Fox isn't fast, but he plays fast because of his decision making. Kakko is getting there. I'm sure he'll continue to work on his skating every offseason, but he's never going to be a burner.