They’d be smart to get him signed next year.
I don’t think he’s wants to be there next year. But man, Ottawa already struggles with attendance. If they lose Stone, Karlsson and Duchene, they need some sort of draw for people to attend.
From a business standpoint, the best thing that could happen is an ownership change (forced).
Essentially, 2018/2019 is a wash, they'll be a bad team, they'll trade their assets for some top prospects, they won't have a first round pick. If they could do an ownership change for 2019/2020, you could really do the ownership:
"This will be a growing season, we are dedicated to improving the on-ice product. The people of Ottawa deserve it, and we really thank you fans for sticking through some of the very tough years of this organization. We want to invite everyone to please show your Senators pride, and support our young and exciting team; we expect to be back competing to bring a Stanley Cup back to Canada, and what better city than our capital. We want to thank our season... blah blah blah."
Essentially get the fans excited for something off-ice. Fire Dorion, bring in Mark Hunter. With Melnyk out of the way, and less of a meddling ownership group, you'd have some excitement in the city. The "Hey, it'll be bad, but man, we have some smart people at the helm now, we can turn it around quick. Look we have Tkachuk in college, he's ready, we have X, Y, Z (Stone, Karlsson, Duchene trades) ready to make the jump to full time NHL'ers. We have a lot of cap for this offseason too!"
Do what Toronto did.