The exponential graph, to the extent it is measuring anything, is measuring progress on LLM benchmarks, which are based on tasks that LLMs can tackle and show progress on.
The set of benchmarks used to measure LLMs do not include things that require significant run-time learning or reasoning (e.g. Chollet's ARC test, although frankly that's a pretty simple test).
This exponential progress will flatten once LLMs can no longer improve along that LLM-benchmark axis (maybe they score 100% on all LLM benchmarks), but this "100% achieved on all tests" won't mean "mission accomplished - AGI achieved!", it'll just mean it's time for a new set of more challenging benchmarks, one step closer to what humans are capable of.
The set of benchmarks used to measure LLMs do not include things that require significant run-time learning or reasoning (e.g. Chollet's ARC test, although frankly that's a pretty simple test).
This exponential progress will flatten once LLMs can no longer improve along that LLM-benchmark axis (maybe they score 100% on all LLM benchmarks), but this "100% achieved on all tests" won't mean "mission accomplished - AGI achieved!", it'll just mean it's time for a new set of more challenging benchmarks, one step closer to what humans are capable of.