On the other hand we are no where near approaching hard limits on LLMs. When LLMs start to be trained for smaller subject areas with massive hand curated examples for solving problems, then they will reach expert performance in those narrow tech areas. These specialized models will be combined in general purpose MoEs.
Then new approaches beyond LLMs, RL, etc. will be discovered, perfected, made more efficient.
Seriously, any hard limits are far into the future.