Although I agree that he probably should get more time, the reality is someone as trigger happy as Abramovich isn't likely to see it that way. He's got rid of popular Chelsea managers before and, despite Lampard's service to Chelsea as a player, I don't think his club legend status will be factored in with regards to his performance as a manager (rightly so).
Their signings are still adapting to the league and country, they're in the last 16 for the Champions League and they're still not that far off the top of the table. But Abramovich may look at the money spent in the Summer and see they're 5 points worse off than this time last season. In his head, there are other managers who could get more of a tune out of Havertz and Werner, whilst improving the consistency of results.
This was always going to be the risk when he was appointed by a historically ruthless owner and even moreso after they spent £250m+ last Summer.