Microsoft has already said that Vista's successor is projected to be released in 2009. Make enough noise now, and Microsoft might actually remove the DRM.
...or just refuse to buy Vista.
The way I see it, the more people refuse to "upgrade" to Vista, the more MS is going to hurt. Eventually, the lost profits will get to the point that MS will remove it precisely because it is severely hurting their business.
In other words, MS will just have to say too damn bad to RIAA, MPAA, and all the other greedy, sue-happy "entertainment" groups out there.
Money does talk, and it has a loud voice, particularly when it comes from your customers.