I'm going to have to disagree with the points about how 3X adventures can't directly be mapped over to 4E without tremendous effort. It's not every day that you get to disagree with some of your favorite adventure writers, so I'll give it a go.

I'm not trying to tell anyone how to do their jobs, but I think this is really being over thought.
Some adventures will have difficulty being updated, and I'd say typically that those would be adventures that have natural pauses and breaks built in to account for resting. The problem is, most adventures don't have that built in at all. Certainly most Necromancer adventures don't have that built in. Building in more space for the battle is more of a cartographic issue, and having interesting battles, well, a boring battle in 3X will likely still be dull in 4E -- and vice versa.
Let's take a look at some existing adventures of different kinds:
When I think about Abysthor, or the Lost City, (two of my go-to adventures from Necromancer Games) I think of largely site based adventures that let the adventurers come and go (largely) as they please, with no time constraint (other than wandering monsters, of course). How any adventure like this would be different under 4E is a mystery to me, since the group would likely handle about the same number of encounters (perhaps one or two more, depending on difficulty) and then leave off to rest.
For a small, site-based adventure, you might have some difficulty, but I know of so many groups who essentially rest after
any difficult encounter to go at it full strength that any internal encounter balance that's been done will largely be ignored. So Larin Karr (another favorite) wouldn't take too much work to convert either.
So then we're left with "time sensitive" adventures. Well, the the last 3X game I ran was the Shackled City Adventure Path. If you recall the first adventure, it's a race through a dungeon to rescue kidnapped children. My group took the bait and decided they were going to run the whole thing and not rest at all until they got to the kids. The problem was they were first level, and there was virtually no chance that was going to work. What I ended up with were several near TPKs as the group said, "I know we need to rest, but we've got to get those kids out!" If anything, a 4E conversion of that adventure would run
better. I would similarly say that the first Burning Sky adventure (where I have both the 3X and 4E versions) runs much better in terms of making the group feel like they can get what they need done in a reasonable amount of time.
So what I'm saying is the notion of adventure design in 4E really doesn't need to be that different from 3X. In fact, it can free the writer from some arbitrary additions they might make to allow a group to rest for a day.
Just my thoughts...and I'll still miss these adventures. I'll be back when Necro makes something for 4E.
--Steve