Well, ignoring that a lot of the cup-winning d-men are gone, it's sort of an oxymoron touting that Forbort/Gravel should get roster spots because they had stellar AHL playoff runs but that the guys who won the Stanley Cup and have had stellar NHL playoff runs shouldn't be guaranteed them. I get what you're saying, and I think some fresh blood and hunger is fantastic, but let's not pretend those guys aren't going to get playing time; hell, we aren't even fully healthy going IN to the season, never mind coming out of it, so they're going to get some NHL experience but bigger AHL minutes, which isn't going to hurt them, and will be here as soon as someone is hurt or struggling. Also, while what those guys did in the A was great, neither of them impressed me here enough to say "yeah, wow, I wish Forbort was on our third pairing right now" (but it is an admittedly horribly small and weird sample size being the preseason, I too want to see them in regular season action for a gauge).
Truth is, most of the guys beyond 8/6/27/3/44 are roughly interchangeable to some degree. Waivers, experience, role, and hell, handedness will all play a part.
I love Forbort and Gravel but like Mersch et. al. they have to outplay someone to get here. They've certainly 'paid their dues' but they also have to earn it with demonstrated ability. HF potential doesn't buy you a Kings' roster spot.