But this research came out mere weeks after the release of gpt-4. That is in itself rapid. If small incremental changes like this continue on a sort of monthly basis, the trendline points towards something that's not a dead end. That's my view of it.
As with most technology there isn't necessarily always a constant influx of inflection points and paradigm shifts. Improvement will likely creep up on us incrementally. Suddenly one day its clearly more intelligent then a human and we can't point to when it happened.