if the future thanos wins timeline is still existing as a potential future poised to become actuality and is the definitive future then no matter how you twist it king thor is a alternative timeline as Galactus was alive and killed by ego the planet in this timeline instead of thanos. if you accept king thor timeline as the definitive future then the thanos wins timeline is going to be the alternative one. both timelines do not mesh as some events have occurred differently in both the streams so then only one or perhaps none of them or perhaps all of the time streams are the true definitive future timeline however you prefer it. it's all head cannon when it comes to what's a Canon 616 future timeline and what isn't.