Depends on how the sales go. They could very well be crying if the trial is offered to the systems whales (the customers that actually matter the most on the platform) and the demo lowers enthusiasm to purchase or otherwise satiates their desire to purchase immediately. The trial is not guaranteed to go one way or the other for every title. There is just as much chance of loosing sales as there is gaining them. And that's not even considering pre-orders which are most likely coming primarily from these users. We'll see how it goes.
I think that in most cases it won't change the purchase intent of the player: before trying most of us already decided if we'll buy it or not.
If we already decided it, I think the demo should be really, really bad to a point we decide to don't buy it. I think will only happen in a very small amount of cases, way smaller than the ones -I think a small percent too, but not that small- where you see a more than decent game that you are not sure if to buy it or not and after playing the demo you buy it.
So I think the overall effect will be to slightly increase sales. Sales do pay bills, the preorders don't.
I think it isn't guaranteed, but in many cases will help a bit. And those where may hurt them, will teach them release more polished games the next time. Which I think in the long term will help them improve and perform better.
And well, the Premium subbers will be able to test all AAA games at launch or almost. I think it's a clear win/win for everybody.