It is quite possible that some trade-offs which held down the growth of intelligence are no longer operational and humans can/will continue to evolve towards even higher IQ.

Maybe, but as you say, it would come at potential cost. E.g. gain of a few points but you won't survive famine, that doesn't sound very good.

Or much more insidiously, gains on an IQ test, at the expense of ability to form/organize/use complex background knowledge (IQ tests are designed to be minimally affected by extra background knowledge).

Practically, of course, the point is moot as evolution is very very slow and humans will self-modify much more rapidly than evolution could provide any noticeable gains.

Yeah, either that, or the civilization goes kaput and it's back to all-natural selection.