Of course they can live with Ryan's contract, especially with Karlsson out of the picture. They can obviously afford it now with Karlsson still on the team. But that's not the point. While maybe he can turn it around, it really looks like you're talking about paying a 30 year old forward almost $8 million a year to score 15 goals a season for the next 4 1/2 years. That's a Dany Heatley-like decline, and Heatley at least was a better player than Ryan was in his prime. If you're a team that seems to be leaning towards a rebuild (which is what it's going to be if Karlsson's traded) and didn't want to pay Kyle Turris, it's a pretty safe assumption that the team would want to get rid of Ryan at all costs.
A rebuilding team (hypothetically Ottawa if Karlsson says he isn't re-signing) isn't trading away multiple young assets to get rid of Ryan. That is literally counterproductive. Brown, White, Chabot, first rounders, etc are the guys they'd be looking to build around not trade away. This is magnified because they're losing their 1st in 2018 or 2019 to the Avs.
Sure, they'd be happier if his contract wasn't so ridiculous but the point is Ryan, while overpaid, is still a useful player. He'd be a top 6 forward on nearly all teams in the league. Even if his play falls off a cliff, he can be helpful to insulate the young guys coming up or whatever may be. You need guys like that during a rebuild.
In like 3-4 years, maybe Ottawa has some studs who are coming off ELCs and they need the cap space. In that situation they may explore dumping Ryan, and it would be an expiring contract or close to it so a lot easier and more palatable for other teams. But now? It's not happening, partly because Ottawa doesn't need to and partly because there's so much term left.