Over on Arqade, they sometimes have "release events" for new, high-profile videogames such as Mass Effect 3 and Skyrim. Most often these are contests, to motivate asking and answering questions about the game. The StackExchange Community Promotion Archive has overviews of past promotions, to get an idea of what they're like. The releases of Skyrim and Diablo III brought major and lasting traffic increases to Arqade. The network likes this, and can provide material and logistical support for such promo events.
We might consider doing something similar ourselves. In the world of videogames, high-profile game releases happen more often than in the world of RPGs, but if the first new edition of D&D since the birth of RPG.SE isn't a high-profile release, I don't know what is. Not only would it help prepare us to be as helpful as possible for the likely influx of new D&D questions, a promo event could also generally raise RPG.SE's profile in the RPG community.
To do it in a way similar to Arqade has done, we would want some or all of:
- a temporary site redesign / art changes
- a competition/prize structure for askers and answerers, keyed off site activity
- social network exposure
- a few network-provided copies of 5e (however they usually do that selection process) to boost our expert base
Etc., which take time and the support/collaboration of higher-ups. If we want to do something like that, we need to float the idea with the community manager team now (because our lead time is only four months now, based on the likely GenCon 2014 release). If the network has the resources and the community team thinks it's a good idea, we can start working with them to develop the promotion's detail right away.