Obviously, the theoretical answer is yes, given an advanced-enough exploit. But let's say Apple is unaware of a specific rootkit. If each OS update is a wave, is the installed exploit more like a rowboat or a frigate? Will it likely be defeated accidentally by minor OS changes, or is it likely to endure?
This answer is actionable. If exploits are rowboats, installing developer OS betas might be security-enhancing: the exploit might break before the exploiters have a chance to update it.