I don't think anyone doubts that we'll continue to make improvements in process technologies until the sun explodes, the main questions are pace and benefits.

Yes, we can create shorter channels using more/different materials. Yes, we can get stronger gate fields using more/different materials. Yes, we can start building vertically and cool the chip using microfluidics. But, all of these things take more time than previous scaling efforts, and are going to have quantum scaling benefits instead of the classical scaling benefits that we had before.

Even now, companies have a difficult choice when switching to 16nm - is it worth the cost and effort? The rules for designing chips have double width each new generation too, making it harder to physically design in addition to the less-manageable transistors. We now have a bad combination of high supply and low demand - new processes double supply due to shrinkage, but reduce demand due to design cost & difficulty.

edit: Newtonian => classical