I personally believe it would only serve to decimate forward initiative in game design not only for D&D as a brand, but ALL of those designer's new works.
Going to a business model that only supports old things could mean D&D stagnates at a point. Every single one of those designers at each of those companies suddenly have to learn the intricacies of every other old edition of D&D just to be able to deal with the numerical tweaks needed to cross-convert things to the various editions. Massive amounts of effort is put into number tweaks, not innovation.
Personal projects of Indie game developers all die. The business of running a core D&D brand takes up all of their time and effort (Since business managers all have to get together to hash out an actual plan as a whole). Designers suddenly stop work on really intriguing non-D&D efforts. Numenera dies, Diaspora dies, All these lines that support different thinking and creativity and artistic design all wither.
Art directors are handed the absolute and solvent nightmare of having to figure out what art direction works for what edition. Many artists of older editions don't WANT to return to do work (DAT, for example). The nightmare only continues when fans start complaining that they don't want to see WAR's work in the 1e/2e conversion/design materials, or Erol Otus working on anything 4e.
And worse yet. Competition dies.
This is, of course, personal opinion. I don't actually have knowledge of inner workings for game companies, but honestly I would see this as an effort in trying to harness chaos itself.
Lastly, those people who are looking forward to 5e because they actually LIKE what they see are ignored. I cannot understand why the voice of a fan of older editions is any more important than those who are looking forward to what 5e could offer. I have yet to have someone give me a concrete reason for this outside of personal preference.
Just my toss of the copper anyway.
-T.J.