I've not heard of any such "rumblings", not that I've been following every bit of news, speculation, and rumor. Hypothetically, one of the natures of an autocrat is that they take out potential competitors, like Lenin did, like Stalin did, like ... . So in
Hypothetical-World, were Putin taken out, there might not be someone who could immediately pick up where Putin left off without missing a step.
This might be good

-fodder for DUpipo, but the real world doesn't seem to be trending in that direction.