Vegas taking Pleky is wishful thinking. Maybe, maybe, they do a deal and take Pleky and a sweetner. But taking a declining 3C making 6 million a year for one more year? Nah. They'll take younger and cheaper so they can sign UFAs.

Think about who else is available for Vegas. Montreal protects 7F/3D/1G:

Forwards: Galchenyuk, Gallagher, Pacioretty, Shaw, Radulov (extension before deadline), Byron, Danault (with the way these two are playing now it makes sense)
Defensemen: Weber, Petry, Beaulieu
Goalie: God

There aren't many other solid options for a team looking at being competitive right away. Plek, Mitchell, Emelin all have one year remaining. DD and Markov aren't resigned after this season (in this scenario). The rest are all AHL players and prospects. Plek is really the only guy that can contribute right away effectively AND is one of the bigger names available to Vegas. They're going to be so far under the cap anyways 6million for one year is not a big deal.

Like if you're going to argue that Vegas would prefer a player like Ghetto, Carr, or Hudon over Plekanec take a look at players exposed from other teams. They have a chance at a half decent roster. Vegas scouts might not get a chance to properly evaluate those three as they have to go over the rest of the league. Plekanec has the name value.

Also, if Emelin is picked over Plekanec, this scenario would still work.