Yes, I think costs go up to cover folks with pre-existing conditions. If the choice, however, is to cover or not cover people with pre-existing conditions, I'll go with covering them and paying more. You never know when it will by you or yours that falls in that category.
I never got the "younger, healthy" generation part of the ACA where college-aged students are being marketed to join the ACA. Now that parents can keep their kids through age 26 on their plans (even if they are married, employed, non-dependent, etc) I would think most of them are already covered and don't need to purchase their own plan. Most age 27+ folks I'm assuming have employer coverage. Or maybe not. Maybe there are a lot of employers that don't provide coverage.
In any case, I think there is very little in the ACA that will control the ever-escalating costs of healthcare that have been ongoing long before the ACA rolled around. There is zero political will on either side to address cost issues. There are far too many fingers in the healthcare pie and it is a complex, patchwork system across 50 states. It can't be fixed with a catchy soundbite solution. I admit that I have wondered if the mandate may be the catalyst that, at some future time, will force us all to figure out cost-control.