It is incredibly depressing to me to walk into a bookstore, look at the RPG section and have no compulsion to make an "impulse" DnD buy. Paizo gets most of my money but they aren't yet as well represented in the bookstores, or at least, when I see their stuff I already have it. I would dearly love WotC to try and win me back as a customer but I'm afraid its not going to happen with 4e or the current management. Nothing they produce sparks my interest. To win me back as a customer they would have to produce material I want again, but, as others have stated, their current approach to the game just leaves me cold.
Still, after thinking about it and reading the whole thread, here is what I think they could do to get my money again:
1) Return to the OGL. This is the big one for me. I've heard all the naysayers about the death of the OGL and how its a lousy business model and yet Paizo is well positioned at the moment exactly because they have whole-heartedly embraced the OGL and foster a creative community that exceeds the borders of their lone company. I am still waiting for a number of people, who, a couple of years back, were patiently explaining why Paizo was making a dumb move and destined to get smaller and smaller, to admit they were wrong.
2) Return to the creative roots of the game. Renaming high elves, Eladrin and stressing dragonborn, and downplaying alignment and getting rid of Vancian magic, and nerfing magic missiles and changing the meaning of dragon colors and altering a host of other stuff, (and doing it all at the same time) was a bridge too far for me. Incremental changes or changes in a specific campaign world are fine but making so many changes as to completely alter the fabric of the game world, requiring nixing old worlds (or blowing them up) is not, in my opinion, a move that fosters continuing brand loyalty (cf. New Coke).
3) After creating a game world I like, and a rules set that is not off putting, I would dearly love to by really good, solid modules from WotC that support their game and which I enjoy reading. Even before 4e, WotC had more or less lost me as a customer because their modules were not fun to read. Paizo had the good sense to realize early on that many DMs never run a module after buying it but will buy them anyway if they are intriguing enough. WotC needs to ditch the Delve format and return to a better module style.
4) Barring all that, rerelease their old 3e books under the OGL and sell them as PDFs and I will buy them. Currently, as someone breaking into the OGL freelance market, I realize I have absolutely no use for books that are not OGL, but I will, even now, when I can, buy old OGL 3e and 3.5e books to mine for OGL material I can reuse in new ways.