Talking about trading Couts right now makes no sense. Nor, I do I think they look to move him next year even if he plays a full season and bounces back to a reasonable level.
You can't retain on him (I mean you could, but retaining for 6 years is a non-started), and I'm not sure any team that would be interested in taking Couts would be willing to take him on for 6 more seasons.
Crazier things have happened, but I have to imagine that he'll be a Flyer for at least 3-4 more seasons. And, I'm okay with that. I have significant doubts he'll be as good as he was between 2015-2020, but I do think he'll still be a very top-6 center for a long time. Just keep in mind, he's very likely going to need ~20-40 games this year to look decent. The goal for Couts this upcoming season is to get through the year without significant injury. It's not really about anything else.