Yeah, I don't ever expect any kind of support for older editions...but if they did, as far as Dungeon/Dragon is concerned, the occasional odd article is probably all that could be expected. Other than that, a basic Character Builder/Monster Builder/Encounter Builder would probably be all we could expect for support. Most likely just core books only though. The kind of investment needed to include all 3E splatbooks/accessories in a Compendium type application would probably be so extensive as to be prohibitive.
But this is all just a purely speculative toy for entertainment purposes. I wouldn't expect anyone at WotC to really care about any of this. I think the chance of older edition support is probably worse than the chances for that proverbial snowball surviving in the afterlife.
Right, its all hypothical.
But if hypothically asking me to spend real money, It would have to be real support. Just thrown a bone and an article wouldnt do it. I'm not spending between 10-15 dollars for the occassional article.