They weren't just stories, it was even confirmed by Tuchel on the club's official website just two days ago that talks over a new deal have begun:
https://www.chelseafc.com/en/news/article/tuchel-confirms-contract-extension-talks
No matter how horrible the Leeds game was I can't see the plan changing. It's been reported constantly over the last months that Boehly and his team have been very impressed by Tuchel and are planning for him to stay long-term with full backing. I think it would take a proper meltdown from Tuchel and the team sliding down the table for them to lose confidence in him. Not saying a meltdown is not a possibility of course, but the most likely scenario is like you said that we will be in a battle for top-4 and Tuchel will sign that extension.
Over the last six months or so there have been some concerns over the performances but for now Tuchel has my full backing, for what it's worth. He's earned himself enough credit in the bank for some dips in performance and the chance to try and build something special at the club. It's clear his team building is nowhere near being done and probably still needs a few new starting quality players to get competitive (a minimum of one new CB this year and a Silva replacement next season, a leading midfielder and a good striker who fits his system).