All bullshit aside, I don't see how Jakub Lauko's presence (or departure) matters one way or the other when it comes to extending (or not extending) Danton Heinen. You like the player, I think he's a plug and easily replaceable.
If the Bruins are interested in signing Heinen to an extension and they agree to a deal before July 1st, he'll be signed. If they don't agree or they aren't interested, they won't. If the it's radio silence between now and July 1st between Sweeney and Heinen's agent than clearly they don't want him back very badly. And if they are interested, telling him that they'd like him back but they have to see what happens with A, B, C, D, E, and F first, well, good luck with that approach.