I'm not seeing the comparisons to Monopoly or chess that seem to be made a lot here, and for many reasons that were listed above . . . its not an apt comparison.
And after Firelance's Monopoly comment, I'd like to say that Risk suffers from the same kind of "If I get this, I win" syndrome. Besides which, simpler rule sets will more likely be subject to minor changes that great ones. . . which often go unnoticed.
3.5 is a good rule set, but frankly, so was the B/X set (just read over it again recently out of nostalgia). Both for different reasons. 3.5 allows for a lot of player creative control mechanically at the cost of play speed, b/x allows for smooth and quick gameplay and the cost of options. 4e looks like its going to try to increase play speed but still retain enough fiddly bits to keep players happy. If it can indeed get rid of the old kludges 3.5 had (which makes DMing for me akin to going for a Masters Degree), but retain the d20 feel and offer the easier gameplay that I (and many others) have been asking for, then I think it is evolutionary in that it is attmpting to combine some aspects of old school gaming with the better revolutions that came from d20, and then top it off with some new twists. The customers will decide with their wallets whether or not WotC was right.
Frankly, I stopped buying suppliments about a year ago because I could see they were running out of things to make "complete" books out of for 3.5. The line has peaked, and any further products would have likely served a very minor subset of the already small gaming community, resulting in negative profit for WotC. And resales just aren't going to keep them afloat. They need to try to evolve, or die as a product. Will they fail? I don't know, but much of what I've seen so far makes me think they will not, and that 4e will indeed be an evolution.
Personally, I'm excited about what they can and will do with it. Having gone through most of the incarnations of D&D myself, I see no problem with the change. I'll still have a spot for 3.5 regardless, but frankly, prep and combat take too long for a game that can already take up quite a bit of time. Fighters suck (thank you CharOp boards for ruining my fun), monster stat blocks look like statistical analysis spreadsheets, multiclassing is kludgy, prestige classes force players to know far ahead of time what they want to be, CR and ECL suck as measuring sticks, required wealth and goodies just to keep pace with the monsters (really, have you thought about the amount of bling your character has to wear?. . . it puts gypsy pimps to shame). the list goes on. So there is lots of room for evolution. We'll just have to wait and see if WotC delivers.
Of course, evolution does not imply improvement and much as it does adaptation to the current environment (our gaming culture). That may mean some good things disappear and other kludges arise, who knows? May also (inevitably) mean they lose some gamers who preferred 3.5.
But I think D&D has indeed evolved, and IMHO, for the better in each case. Some things were better in older editions, sure. But D&D has evolved and become a better game for it.