If you're short of 20 minutes to read it then there's a six minute video, which is an easy watch:
There's also a slight tease in the wording of one paragraph. From the article:
Cutler stopped managing the entire NT project in 1996, but continued to lead the kernel development until 2006. In March 2005, he completed one of his “most gratifying pieces of work” at Microsoft when, partnering with AMD, he helped develop the AMD64 architecture (64-bit extensions to the 32-bit x86 architecture) and led the effort to ship the first two x64 64-bit Windows systems (workstation and server). At the time, some questioned why Microsoft developed a 64-bit system; today most computers are 64-bit systems and even our phones will soon have a 64-bit operating system.
The wording is slightly ambiguous (does 'our phones' still refer to Microsoft-branded devices?) but it does seem as though the next logical step for Windows 10 Mobile is a 64-bit variant, to be shipped in next-generation hardware in 2017. Perhaps.
Anyway, make sure you read through the complete piece, it's fascinating background on the smartphone industry and one of its biggest characters.