There was a Daily Kos article on Thursday titled “Mueller’s grand jury conducts rare Thursday session, could be sign of Friday indictments”
Stone is mentioned multiple times in the article and comments. If a bunch of internet keyboard warriors on Kos could guess that Stone could be indicted on Friday it is not a stretch to think that CNN could.
It makes the question even more urgent: how is it that Kos is clued into the workings of the Mueller Grand Jury?
And if it was already 'out there' and Stone hadn't fled, why not just ask him to surrender himself with his attorney?