The real opportunity would be for Linux improving the UI for the vast majority of users
As far as UI's are concerned, Windows 10 being released looking a whole lot like Linux Mint might not be an accident -- Microsoft has been known for it's rather user friendly UI's for years .... why do you suppose they suddenly decided to emulate Linux in that regard? Could it be that the simplicity of that particular Linux distro struck a nerve? Maybe ... maybe not ... who knows? Microsoft is well known for ... cough ... borrowing ... cough ... cough .. systems elements and design from others over the years, I'll cite IBM and Apple in this regard.
UI's aren't really the problem ... going after 3rd party peripheral builds for existing hardware on a Microsoft build is, however.
As long as Microsoft expects it's end users to go after peripherals in the wild, it will always be an inferior system .. Mac and Linux have rather closed and extensive repositories with peripherals that have been thoroughly vetted.
Microsoft has done more to advance malware over the past 10 years than both Linux and Mac combined over the past 20.
How many times has the Windows user had to try and find sound drivers, for instance, for an onboard system that just updated to a newer version build? And with that, how many instances have ended with bundled and unwanted software as a result?
Most people have no idea who made the hardware, because as far as they're concerned, it's all Microsoft .... so anything that has Microsoft written into the description should work.
As far as Saas and Microsoft systems working better together? One might make note of the fact that as long as the Microsoft OS contains elements of Windows 2K and XP, with all of the related deprecated writes and work-arounds that they contain, the entire system will remain the same as it is today.
Microsoft systems will continue to be better and more robust as long as there are those out there that believe it - I used Windows for years, but I got tired of the bugs, slow performance, and continuous patches -- You shouldn't have to reboot a system every time an update rolls around -- Updating should be done on the fly ... light and easy ... without bogging the system down during a heavy workload.
Hassle free computing should be the order of the day -- It's hoped that one day Microsoft will figure this out.
A rule of thumb with regard to just how well Linux might be doing? Just take a look at Windows ...
The only cavet being that you've got to know both systems well enough in order to see who might ahead of who, or who might be copying who -- currently, Microsoft in on the short end of the stick