Yes, finally we are going to see a shift, but their 'dominance' is not going to necessarily change that much in some kind of 'step function'.
I suggest that Siri is about to get a lot better, and act more like we wanted it to act a decade ago.
As amazing as ChatGPT is, it's actually not that useful for most regular people other than as a more human form of search.
I think Google results will improve quickly enough that whatever MS does will seem novel but not necessarily have some kind of huge consumer impact.
We'll see search for company info and help directories get a lot better.
Remember that both MS and Google are 'etablished' companies, the later a bit slow moving and not firing on all fronts.
Why would anyone think a company that can't get Skype to work, is going to marvel the world with some 'new thing'.
OpenAI folks are on a roll, rapidly trying to make cool looking experiments, focused on 'wowing the world' not on direct revenues. Making that translate into products is another dimension altogether.
The most interesting stuff will come from startups.