I don't follow how Ramsey theory suggests a limit. I do agree with you that there is a limit - governed by the laws of physics: more compute requires physical infrastructure (for which we have finite raw materials) and space - and the larger it gets, the more the speed of light governs processing speed. However, that limit is so astronomically higher than our current capabilities that it might not have any practical impact any time during our lifetimes.

Ramsey theory says that as a data set grows, spurious correlation increases. At some point, adding a new data point is more likely to give a spurious correlation than a valuable piece of information. That's where the limit would be.