Considering the insanity of the AI arms race going on now, and the incredible sums of money be thrown at any slight advantage, is there any reason to believe that any meaningful AI breakthrough would be openly published for anyone to leverage?

These folks are MIT, so citations are valuable to them. Citations convert into prestige, academic career progression, or a favorable exit from academia into industry.

Also, I don't see why you couldn't patent this if you wanted to monetize it.

I know the frontier “labs” are holding back publications.

I don’t think it will last among researchers who think beyond production LLMs

I would say yes.

The reality is that the money being thrown = the time of humans. I guess compute as well, but in terms of people doing innovation - openly published things are the same thing, minus the money.

I do sometimes wonder -- if the transformers paper wasn't published, what would the industry be like? Would the same ideas have been put together in almost the same way weeks or months later somewhere else?

The inventor's grace period under first to file changes still gives them/their university a year to file if they publish openly.