If dallas has any intention of keeping Bourque at all, they are certainly prepared to pay him 4.5 mill already.
If not, he'll be traded before july 1st even hits.
This isn't Broberg where an AHLer/7th D is getting 4+ mill.
This is a 40 point roster player.
4.5 mill on a 104 mill capwould be a normal contract for him if not on the low end, not the kind of overpayment that makes an offer sheet work. Especially for dallas and bourque where he'd be an RFA again next year, it doesn't even provide him an incentive since it doesn't walk him to UFA, give him security, or give him a lot of money
eg 4 mill for a 7th D
2+ mill for a 4th line, 9 point forward,
6+ mill in a 83 mill cap for a 20 point forward.