Not unreasonable, but keep in mind that the core countries in that graph have been replacing their own profits with the profits from production in "developing countries," a countervailing tendency that is about to run out. As well, they do things like count finance industry activity in GDP, so there are probably some major discrepancies in the official ROP statistics too.
Another countervailing tendency was the addition of computers to business processes, which increased the ROP by reducing non-productive business expenses (such as accounting, financial transactions, etc). The flipside of this is that computers are also going to continue to replace actual workers, especially with highly expensive AI technology, so the ROP is going to take another hit.
Capitalists could obviously try to keep the whole system running even at 1% ROP, but it would be highly unstable, and the other major reckoning, global warming, is basically going to wreck it.