Microsoft may have to make an extremely compelling case for Windows Phone 10, and do so immediately, for it to have any chance of success after its general release late this year.
But what constitutes "success" for Windows Phone 10? How much market share would it need to gain to remain a realistic player in small devices into 2016?
Even though Windows Phone 8.1 gave Microsoft a boost in phone sales, the company still lost market share, Dawson said.
"So the first job is to turn that shrinkage back into growth," he said. "I don't think Windows Phone becomes a really significant mobile operating system until it's two or three times the size that it is now.
“I think if it were to double its installed base over the next year-and-a-half, that would be a massive achievement.
“But I think it's actually a longer-term project to make it really relevant, and I'm still not convinced that Microsoft has the tools it needs to make that happen."
Microsoft shouldn't extend its vision for how Windows 10 functions too far into the phone, Rubin warned.
"History has shown us that people don't want a traditional PC experience on their phone," Rubin said.
"That's what Windows Mobile was all about. They don't want it on their TVs; they want more of a leaned-back, video-centric experience."
For too many users and probably more would-be users, Windows 8 is genuinely disliked. The last Microsoft OS to receive such disdain was MS-DOS 4.0.
In 1989, when Microsoft shifted its strategy from producing DOS and OS/2 to producing Windows 3.0, the company explained the reason for its shift as a result of listening to its customers, and recognising that the market had reached an inflection point.
If Windows 10 fails to prove Microsoft has not only listened but contemplated what it heard, at the very least, it may find itself extending the support lifeline for Windows 7 while it watches the rest of the world move on.