I don't condone, or participate in illegal PDF's. Still, there has always been illegal PDF copies of the 3E books going around the web. Even well scanned versions. It is very unfortunate that people are thieves, but theft is a reality every business has to just live with.
So the effects of these 4E pirated versions are going to be the same as always, hopefully very minimal, and maybe even balance out a bit in convincing the thieves to buy the actual books. Even though I would say its more likely to convince them to shop lift the hard copies.
Besides, pirating copies isn't worth ever getting caught. Yes, they won't come knocking on your door looking for them. They might come knocking because of suspected drug use, other criminal activity, or vicious ex-lovers and friends reporting you having them.
No pirated PDF is worth spending years in prison and/or paying thousands of dollars in fines. Plus if you work for any level of government, especially if you are a military retiree, you can also lose your retirement.
So pirating is a really, really, stupid thing to do.
However, we humans aren't known for our over all level of intelligence or foresight.
Just do yourself a favor, don't pirate! Not only is it wrong, but its not worth the price you will pay if you ever do get caught and charged.
As for me, I am waiting on the 4E SRD. That might, maybe, possibly, convince me to buy into 4E. Plus its legal.