Let's posit for a minute that the core of D&DNext cleaves more closely to 1e-2e-3e feel than 4e. Heck, lets even say closer to 1e with a bunch of modern innovations mixed in, like the best of the OSR games. I can see a problem with this. There are a ton of new gamers who have entered the hobby since 3e, and they'll have absolutely no idea what D&DNext is shooting for. Some of the decisions that cater to nostalgia may seem odd to them.
Thus, the re-release of the 1e books. They give newer gamers a chance to see what's come before, and (hopefully) they provide a positive basis for comparison with the new rules set. It's sort of brilliant, actually, because this is a case where everyone wins.