Dungeons & Dragons Legacy Edition
If it was up to me (and I know it's NOT), I would create an edition of 4th Edition core rulebooks that combined a lot of elements of the past editions. This wouldn't necessarily be a "5th Edition", but it could DEFINATELY buy WotC some time before the pressure was on.
How would I do this?
I would make all of the artwork VERY old school - kind of like what they did with the Red Box. I would also go back and make sure the interior layout of the books were more like 2nd and 3rd Edition. I know it SHOULDN'T matter, but the 3rd Edition book's aesthetic really SHOWED me what this game was about before I read one word. Subtext: parchment paper!
I would also poll as many D&D fans as I could from different versions and find out which Races and Classes were their favorite. I would then take these into consideration when putting them into the PHB. I would try and put in TEN races and TEN classes - boom! I would also include the NINE alignments. BONUS: This would also give WotC an opportunity to put the updated 4e rules back into a CORE book - not just a paperback compendium (which we use HEAVILY at our table - thanks!) I would also do a character sheet that SHOWED all of the old skills, but sub-categorized them under the one skill that they pertained to. Example: sense motive, etc are all under Insight now.
I would then do the same thing with the DMG and MM. Keep the updated 4th Edition mechanics, but make sure that everything else is sort of a "greatest hits". The Legacy DMG would also give you the opportunity to put in the updated Skill Challenge rules.
Giving D&D players of all ages and all editions a say in some of this stuff would be an amazing PR strategy. It would be a way to say, "Look, we're not going back. There's just no way. But, we haven't forgotten you and we still want you to feel welcome to the table in 2011. Just TRY 4th Edition." Because frankly, right now, Wizards is doing nothing to reach back out to the thousands of people who have dropped D&D for Pathfinder. You would think someone would say, "Hey, we need to do something to appeal to all of these old school gamers or we are going to lose them to Paizo FOREVER."
Like I said, this would be a HUGE undertaking to release three new books, but that's all it would be -- three books. WotC would go on as usual after that. Personally, I would pay whatever I had to pay to get my hands on some limited-edition retro junk like this.
How would YOU do it?