Reilly Smith will be like Kris Versteeg, an inconsistent 40-50 point scorer. During 5 years, I'd expect Smith to probably put up his contract maybe 2/3 seasons out of 5.
Hayes will or should be bought out.
The situation with Hayes is a little mucky.
The Bruins have to leave two forwards unprotected for the expansion draft in order to meet the qualified players. That would be Hayes and Beleskey. If you remove Hayes prior to the draft, Marchand is the only player that qualifies (no NMC - under contract - and meets games played) that fits the criteria. (this of course barring any trades that brings someone else in that would meet that criteria)
I was asked elsewhere if the Bruins can use the second buyout window on Hayes.
The simple answer is: No!
While the Bruins have several players that are arbitration eligible, and it would take one of those players going to arbitration to open up the second buyout window, Hayes doesn't make enough money to be able to be bought out in that window.
A player eligible to be bought out in the second window has to make a minimum of $2.75 million per season. (2016 numbers based on league average salary and will only go up for 2017).
There is only one option for the Bruins:
The buyout period is the latter of June 15th or 48 hours after the Stanley Cup is awarded up to and including 5:00 pm on June the 30th.
The expansion draft is June 21st. You keep Hayes up to the expansion draft and expose him. If he is not claimed by Vegas, they buy him out between June 22 and June 30.
As I said, barring another move, you keep him. The cost of moving him prior to the expansion draft could be huge to the Bruins. The good news is he has met his games played qualifications, so with a healthy squad, they can sit him as long as they want.