Successfully making a 7nm chip doesn't mean it will ever be cost-competitive with a 28nm or 16nm chip. Per-transistor cost isn't going down anymore, so these new processes are only going to attract customers that are willing to pay more for lower power or higher performance. It's no longer the case that the whole product line will be brought forward when the fab capacity becomes available.
It was only this spring that AMD finally removed 40nm GPUs from the low end of their product line. They'll keep selling 28nm GPUs until the fab equipment breaks.
But if you add the energy costs, it makes financial sense to move to newer nodes. Maybe we need some financial innovation that charges a part of the chip in small installments that you won't feel , because of savings ,while also supporting moore's law ?
Then you get the option. Today you have a much more pronounced choice between cheaper more power hungry AMD parts or expensive power efficient Intel ones.
In 2020 we will very likely have the choice between 7nm expensive high end CPUs and 14-16nm midrange parts, and budget phones / tablets/ low end cpus will be shipping 20nm. And we will still be using todays 24/28/32/40/45nm plants for various other circuits.
It was only this spring that AMD finally removed 40nm GPUs from the low end of their product line. They'll keep selling 28nm GPUs until the fab equipment breaks.