Ever since we drafted Yakemchuk and Jensen solidified himself as Chabot's partner, any need for EK disappeared. EK below $3 million on the third pairing is fine, but anything over that to have him play behind Zub and Jensen is wasted cap space. We would have to move Norris as well and kill centre depth that we aren't getting back in any situation where we get EK back.
I'll welcome EK back on a league min contract in a few years but right now it doesn't make sense
I don't think for on ice reasons that an EK trade makes a lot of sense, but if I can play devil's advocate:
Yakemchuk's timeline is pretty close to EK's timeline to get phased out of the lineup. They very clearly do not want to rush Yakemchuk, otherwise he would have been on the roster out of training camp when we had a glaring need for depth on D, and he had a lights out preseason. There is no guarantee they envision Yakemchuk spending the entire year on the team next year. So it potentially would be a situation where EK and Yak only overlap for however many games Yak gets before being sent back to the CHL, and then for the last season of EK's contract (assuming he plays out the entire contract, which with his injury history could go either way).
They very clearly want out of the Norris contract if there is truth to the perpetual trade rumours from the last 2 years. If the reports that the Penguins will retain on Karlsson is true, they can potentially fit a 3C and Karlsson in at close to the cap hit of Norris. So that means they would have Stutzle/Pinto/Greig/Amadaio and another C as options to fill the top 3 center spots. I don't think center depth would be a problem.
You know what is a problem with this team? Scoring. Despite his drop in overall play, that is something Karlsson excels at, creating offense. He has also shown that at least for a short period of time, he can excel in very structured defensive systems. Ironically, the peak of his career came under a suffocating systems coach.
The most intriguing reason for them to bring back Erik Karlsson is that at the end of the day this is an entertainment product that relies on fan dollars. How many extra season ticket packages or sponsorship deals are they attracting by bringing back one of the biggest local superstars of all time? How much positive goodwill does it bring to the current ownership group (as long as they don't put him in half a Nordiques jersey....) to be able to effectively write one of the biggest wrongs of the Melnyk era?
(Yes, the trade worked out - and no sane person would undo it, but the series of events that lead up to the trade, and the trade even being a possibility is what is perceived as being negative.)