Please don't be true...

that puts vegas in an awful cap situation you better hope eichel gone till playoffs else teams will take advantage of you when you need to dump dadonovs contract to fit in tuchn pax and eichel. But eichel also missing all season is bad too because it gives him no time to develop chemistry or learn vegas's system. realistically if you trade for eichel you will have too pay the extra price for buffalo to take dadonovs contracts and maybe retain 1 mill of eichels contract.
ideally i see the trade being

vegas receives:
Eichel (1 mill retained)

Buffalo Receives:
Smith
Dadonov
Krebs
Chayaka
22 and 23 1sts
24 2nd
22 3rd
or you replace chayka and 24 2nd for brisson

Pretty sure buffalo refuses to retain a dime of Eichel‘s contract for the next five seasons. Vegas would have to commit franchise suicide to make an offer Buffalo where would not say no to retention.

ya i have heard that to but realistically buffalo is gonna have to start budging soon as once eichels nmc kicks in buffalo will be committing franchise suicide when eichel and the nhlpa forces them to make a trade for half the value they want. buffalo won't be competing for atleast 4 years so i don't see why the 1 mill per season is such a big deal especially if they are getting assests for the retention also helps them just that tiny bit stay above the cap floor. until skinner and okposos contracts off the book they might aswell just retain for futures and start building an even stronger prospect pool they won't be signing no big free agents until then.

IMO no retention claim just is posturing.
Buffalo is currently $5,000,000 over the floor with $15,000,000 applied from 3 players on IR (Jokiharju, Mittelstadt and Eichel)
If Jack is traded and $5,000,000 is retained, IMO they could still make the cap work.
Next year, they could have as many as four players in their first year of ELC.
They may need the retention to reach the floor.
When the ELC expire they could offer the players one year Bridge deals so they could be signed to longer term contracts once the $5,000,000 retention expires.
I think Smith, Dadonov, Krebs, Brinson, 22 and 23 1sts and 22 3rd could be the deal.
Dadonov and Smith would be traded soon after the trade or part of a three way deal.
What do I know I am just a casual fan who listens to other comments.

I was close