It's likely college will be free in 15 years
I think it's a pretty safe bet that by the time my kids are college aged that they will be able to attend college for free.
I want to support my children rather than my adults
I'm not saying that we'll kick our kids out of the house the day they turn 18, but I do want them to have the skills that they need to make a career by that age. Some people think this is a bad goal, but I believe that the specific value of a college degree is overblown for many people. Unless my kid wants to specialize in a technical field where a college degree is a minimum credential, I don't believe that college will aid them in their career.
However, career ready kids don't just happen. To have a career, you need to have skills. You need to create value for other people, you need to know how to market yourself, you need to have some level of proficiency. These are things that kids and teens can learn, but it requires upfront investments of time and money.
We don't have unlimited time or money, but this is my theory. We can save $200-$300 per kid per month in a 529 plan, and then if our kids go to college, they can use it (if college isn't free by then). We could alternatively spend $200-$300 per month helping our kids develop their passions. If we do a good job helping them develop their passions and hone their skillsets, they are likely to be career ready.
The second option sounds like a lot more fun, and it sounds like an option that will serve our kids no matter what.
The college price bubble will burst
The government is great about pretending that problems don't exist, but private lenders are not going to lend to poor credit risk students, and the costs of college aren't going to continue to rise without lenders.
Additionally, online college programs already exist, and people can obtain degrees for less than a quarter of the cost of public in state tuition. The only thing getting in the way of the proliferation of these low cost programs is snobbery. Seriously, online education is great. About 90% of the useful information that I know came from the internet. If college isn't free, and my kids need further education, I'll definitely push them towards online schools that they can pay for themselves.
If all else fails, getting rich never hurt anyone
529 contributions are after tax contributions, and they need to be used in about 18-22 years. We shouldn't aggressively invest if we're going to use all the money in 18-22 years (no 4% withdrawal rule here), so we're probably better off growing wealth outside of a 529 plan. We can do things like buy rental houses, or invest in after tax accounts or in our own businesses.
At the end of the day, if we do manage to get rich, we can pay for college from cashflow or by drawing down some savings.