Case in point, I'm not planning to watch Fringe this season - I'll buy the DVD later. Yet under Nielsen's decades-old criteria, if I'm not in front of my TV tonight at 8 or whenever, I don't count. Yet, frankly, there's zero difference between me deferring viewing a show for X number of months till the DVD arrives and if I'd videotaped the thing and watched it a few weeks later. And in most respects it's better because I'm paying for the privledge.
As long as TV is dependant on advertising revenue Neilsen ratings and the like will continue to be predominant. Sure you might buy Fringe on DVD down the track which is money towards for the producers, it's not producing revenue to the tv network that shows it. When it comes to setting the pricing for advertising next time, the ad agencies will look at the number of people who watched then and there.
Anyone who buys DVDs or DVRs thus skipping ads is irrelevant to the situation.
Or to put it simply, you deicision to by Fringe on DVD might help them make the next season but it won't guarentee when or where it will air.