If renewables actually did cost less the entire economy would be switching to them without any prompting. But they don't, they're only cost competitive by either subsidizing them or making fossil fuel alternatives artificially expensive.
1) Electricity is far from a free market as is the underlying premise of your argument. You do realize that for about 60 years from 1949 to ~2000, 94% of energy subsidies went to coal, oil, gas, and nuclear, right? And that to this day we still subsidize those industries, right?
Furthermore the negative externalities of things like acid rain, smog, and water pollution (not just fracking but also things like tailings) are not being accounted for with fossil fuels, though to be fair you should also do that with waste products from solar/wind turbine/etc. production.
The energy market is NOT a free market due to these distortions. Congress meddles with it at every turn, just like with agriculture and how heavily subsidized corn is once you factor everything such as water subsidies and the ridiculous ethanol mandate.
2) The flipside of 1): Renewable energy costs are plummeting as technology keeps improving, whether in solar efficiency or battery storage tech. Also, a lot of the price of power is due to transport lines; with distributed generation you save a bundle on distro and transmission lines.
Look at Africa for instance. They aren't burdened by legacy costs of stringing wire. They don't have as much land-line phone service or electricity service because that's expensive and requires a lot of density. So what they've found is that in some parts of Africa it's more economic to simply use a solar panel and battery. Similarly, mobile phones are way popular there because it's cheaper to wire up transmission towers than each individual home.
3) Energy policy should not be short-sighted. As hydrocarbons become harder to extract, price WILL keep going up. A lot of numbers people throw around #s about how we have x number of years of coal/gas/oil at present rates of consumption, ignore how we are consuming such hydrocarbons at an increasing rate, and how
the low-hanging fruit gets picked first. The cheap stuff gets used up first and as we get more desperate we reach for higher and higher fruit like arctic oil or deepwater oil. Same for gas, nobody was desperate enough to frack shale for gas until 2004, and while you might hear talk of "cheap" gas, historically gas has been cheaper than it is today. Similarly, the high-grade, easy to reach coal got depleted first.
Long story short, hydrocarbon costs will rise more as more people (literally, more population) uses more energy per capita. Rather than wait till the last minute, we should be trying to get ahead of the curve.