To have me as a regular customer again, Wizards would have to do two things. First, they need to apologize for treating their customers like thieves. Short of a full apology, it would be nice if they restarted PDF sales, stopped trying to screw around with publishers trying to use material that WotC offered to let them use last time around, and loosened up the GSL. Second, they would need to offer something I wanted to buy. I don't like 4e, and I'm not going to, so their best bet there is hoping that in about 7-8 years I'll be interested in upgrading to fifth edition. Honestly, 4e rolling out when it did was so inconvenient I'm not sure I would warm up to a new 5th edition if it came out too soon. It would have to be the pinnacle of game design to pry me away from PF and older d20 games, to say nothing of GURPS, etc. I would be interested in buying some minis, if they started making something that didn't look like doodoo. I can not think of any reason why I need a My Little Ponicorn or a Weapon X Super Skrull Troll, and most of their PC minis have looked like something pooped plastic, and that's aside from the questionable utility of female dragonborn rogue minis (seriously? are we there already?).
I'm not ruling out the possibility of them winning me back in some fashion. Between 3.0 and 3.5 there was a change in art direction, and it's possible the 4e minis and such might start looking better to me. I wouldn't mind more 3.5 books, but first of all, there will not be any, and second of all, anything that looks like it's designed to directly compete with PF will not be getting my dollar. If WotC decided to publish a Pathfinder compatible monster manual full of non-OGL monsters, I'd probably buy that. Ha!