I'll hold off on this until it's cleared up.
They've been oddly specific in detailing only a few sources for Marks (Daily Heroic Story Chapter, Daily PvP, Heroic Strike) - but then quickly reassure you there's no cap on weekly gains.
I want to doubt this "no cap" refers to the potential for making more via legendary dismantling.
All signs seem to pointing that it does.
It seems to make sense.
Reducing progression speed impacts like 10% of the hardest of hardcore daily players. Destiny is not a microtransaction game, so it doesn't need to cater to whales.
What it does want to clearly do is make your acquisitions matter to you.
Now that is a different track then a super high level player feeling "stuck" because they raced through everything they could for the week. Their decision to spread these limits across all three characters also points to this. They don't want people to feel like they need three characters to get their max weekly loot.
This is, I believe, what Bungie wants your Destiny end game week to look like. You got a Legendary on Tuesday. It's wonderful, or it's not. You spend a few hours every day filling out the slots with mats and XP. Or you do some activities to gain XP so you can use the loot. By the next Tuesday, you've spent the week with your new gear and it means something to you.
What your week looks like now: Nothing to buy from Vendors, one thing to buy from Xur, you're maxed out on marks and mats. Your gear is a blur of numbers and perks, and god help you, even Fatebringer is boring to you now, so much so that the Strike stream hand cannon was annoying just from the damn sound of it.
I prefer the first one. It's different, and it will certainly steer the game away from where it is now for high level players, but I think it's the right decision.
What drew me to Destiny at the very beginning, was the promise of that great loot. The way the UI made it more appealing than a Forza Motorsport car. I want that back. I want, like they said in EDGE, every drop to mean something.
For that to really be true, they have to pump the breaks. It will mean less stuff that means more, and I honestly prefer that instead of the situation now:
More stuff that means less.