Intentional? It's a tough call but it's hockey, so no call is the best approach.

https://www.youtube.com/watch?v=Nj4PoDrqv-E

Not a tough call at all. He was pissed about the hit down the ice and probably the fact that the refs missed it. Sure he has his head down for a bit, but not for a good 2 feet till he gets to the ref, who is obviously not a Nashville player, and he launches into him with while raising his arms and stick.

20 or 25 games, though knowing the NHL, it will be 5.

How is this a tough call? Of course it was intentional. He'll be suspended

Rule 40.2 of the NHL rulebook a player will be suspended a minimum of 20 games if he “deliberately strikes an official and causes injury or who deliberately applies physical force in any manner against an official with intent to injure, or who in any manner attempts to injure an official”.

Rule 40.3 a minimum 10 game suspension if a player deliberately makes contact with a referee without intending to injure him.

It looks intentional to me too. However, If I was representing Mr. Wideman at the hearing:

"My client had just received a head injury and was attempting to return to the bench as quickly as possible during play, since the puck was coming back to his zone. In doing so, his direct line of return was impeded by the linesman, who was skating backwards, unaware of the eminent collision. Mr. Wideman tried to make a move to his right, but in a defensive manner, my client lifted his stick to save further injury. As it is not the duty of the linesman to call penalties, I can not understand how this can be construed as malicious, or believed that Mr. Wideman would hold any animosity towards a linesman if he did in fact believe there was a missed penalty call."

For the record, I think there will be a punishment.

https://youtu.be/b07sactDEKU

Suspended and awaiting hearing... Tsk tsk!

No misconduct on the play, so his suspension won't be tied to rule 40 posted above. It could be anything.

I think 10 games seems about right, unless Henderson really wants to make big deal of it.

Henderson and Wideman occupying the same space was just a matter of bad timing. Once they did meet, Wideman went way overboard probably due to being frustrated/scrambled by getting slammed right before. But, it's not like he started towards the bench with the idea of laying out a linesman. He was late on the long change, Brodie was already on for him and the play happened to come right there putting Henderson in the way of Wideman getting off.

I agree with Kerry Fraser's take, basically that contacting Henderson was a matter of chance and unavoidable, but drilling him in the upper back was wildly unnecessary.