EK didn't play like Method did & he gives him all kinds of props, Mackar gets all kinds of props too for being a great D who doesn't play like Method. Brannstrom is on the 3rd pairing for a reason & as long as the top 4 don't get hurt will stay there. He isn't getting PP time because Chabot, Sanderson & Chychrun will get that time along with their six forwards who lead the team in scoring. Brannstrom is yet to show the offence to be on the top 4 & is still an injury replacement player.
I think it is going to come down to what the team values & think it needs on that 3rd pairing. Kleven brings an element of size & grit that the team need on the backend with Holden likely leaving & Hamonic winding down. It's an element that DJ values & that the team is being built around. Whether Kleven is NHL ready though is another question, but he sure looked comfortable in the few games we watched. JBD is likely also going to be on the team given his waiver ineligibility although I think as a 6th/7th D.
It won't surprise me if Brannstrom is still on the team next season & starts in Ottawa & Kleven in Belleville, but I also won't be surprised if he isn't & Kleven starts in his place. I think it could go either way depending on what happens this summer, I guess we'll see.