Well, sure, silo-ing is one way to handle this. But I think they've said that Next won't have silo-ing.
X before Y is just like hit points - X hit point to win, Y hit points to lose - but with the players rolling all the dice and every hit delivering 1 hp. There's nothing wrong with introducing a critical system as well (Essentials has something a bit like this with its advantages system).
The only way it's like hit points is if you institute a rule that every time you miss with an attack, you hit an ally. If you add another warm body to your team in combat, your team is more powerful, period. You have the
option to spend resources keeping that warm body alive, but you don't
have to; PCs in desperate straits can let their teammates drop and focus on victory. If you add a warm body to your team in a skill challenge, you may well be worse off for it.
But regardless, I have never seen a skill challenge that was either fun or believable without a hefty dose of DM fiat to make it work. Here's what I've seen happen any time the DM runs a straight-up skill challenge:
#1. Each player plays "Mother-May-I" with the DM to find the highest skill modifier the DM will let her use.
#2. Players go around the table, try to find different ways of phrasing whatever rationales they deployed in step #1, and roll d20s in turn until the DM announces success or failure. The DM gives a contorted, unconvincing narrative whose obvious goal is to string the players along until they reach the prescribed number of successes. Now and then, the DM may decide that some player's excuse for using Skill X has expired and send her back to step #1.
What we have here is a mechanical system which is both rigid and mindless. There are no decisions to make, and no way to think "outside the box" and get an advantage. Mechanically, all you do is sit there and roll your best applicable skill until the challenge is over. The DM's task is to cloak this tedious reality from the players with narrative flash and dazzle. But D&D players are pretty smart, and in many cases they've been on the other side of the DM screen. It's not hard for them to figure out what the DM is doing.
The only way to make it fun is to either a) make the system less rigid (if you come up with a clever idea, you can get an auto-success or even multiple successes), or b) make it less mindless (different skill choices have different effects and the mechanics of the situation change as the challenge proceeds). The sample challenges in the DMG take the latter route, which says something about what the designers thought of their own system.