Can graphics keep evolving? How? For how long?

[Pajderman]

We are still far from the ceiling from a technical standpoint. But the cost of developing games maxing the high graphics capabilities we already have is to steep for most studios.

Getting to perfection is very costly. If it takes 100 hours to reach 80% of max out it will take another 100 hours to reach 90% then double the already spent time for each extra 1%, until 99%, then another doubling for each extra 0,1% improvement.
It is not exactly like this, but it will be more difficult to reach a noticeable improvement the closer one gets to the optimal of any field. And true perfect is probably a practical impossibility.