Nebulous
Legend
I'm thinking that it's not really that hard to convert as is.
A lot of material is extremely similar to 1E and 2E. For example, it'll take all of a minute to come up with an equation to convert THAC0 to AC and once you have that equation, it doesn't change.
Yeah, it's not that difficult. Which is great, because it doesn't invalidate all those great adventures. I'd highly recommend someone running Red Hand of Doom in 5e. Hell, you could probably port over Keep on the Shadowfell and have a great 5e dungeon romp.