they might be able to narrow the gap with Apple wrt software, but I don't think (at least in the US) Garmin will ever gain marketshare vs. the Apple Watch, especially now with the Ultra for the simple reason that Garmin just cannot offer an equivalent experience on iPhones because of Apple.
We desperately need antitrust intervention to force Apple to open up iOS to allow other smartwatches to take advantage of the same APIs that the Apple Watch does.
If that happens I think Apple will quickly find that they cannot compete on an even playing field.