Though it's speculation, I would assign the probability of evolution continuing to work (and improve) on the human race as pretty high - what gain does the human species have in preserving humans from the 21st century indefinitely, when 23rd century or later humans are better?

Improve humans in what respect? Do you think that high intelligence is positively correlated in modern society with number of offspring? How about moral character? More attractive people are certainly seen as more sexually desirable, but do they have more children?

Evolution doesn't improve species, it increases their fitness within a particular environment, and it only does so in response to selection pressure. It doesn't matter how wildly successful a person with an IQ of 220 would be, if people with higher IQs do not have better odds of producing surviving offspring, evolution will not make humans smarter, and the same goes for any other measure you might apply to the worth of a person.

In any case, most of the difference between a person now and several generations from now will not be genetic, unless we start tinkering around with human genomes ourselves. Other adaptation mechanisms, such as memes and technology, change much faster.