In a short post on the Stardew website and social media today, the game's creator Eric 'ConcernedApe' Barone has revealed the release date for the Stardew Valley 1.6 update on console (and mobile devices) will be 4th November 2024. This console update will "release at Version 1.6.9", which comes to PC around the same time.
Barone has confirmed this update includes the Nintendo Switch platform. He also reiterated how he's always released these updates on PC first, as it's "sort of" a "beta test" to ensure there are no critical bugs, which could be a much bigger issue on console without the ability to patch problems immediately.
As for whether or not you should start a new file alongside Version 1.6, you can still experience "almost everything new with your existing save" but there are "some" new things, like in the first year compared to the follow up years.
You can view the full changelog for the Version 1.6 Update on the official Stardew Valley website. As also mentioned, after this is complete, Barone plans to finish his next game Haunted Chocolatier.
