At that time software's AT&T style winner-take-all and network effect lock-in was still not that obvious. The PC was not yet the golden standard for desktop hardware and words like minicomputers and mainframes were not uncommon terms.
So it was not a safe bet in 1996 that Windows and Microsoft would still exist and be a big market player in 2020.
So I'd say 2020 -> 2040 Microsoft is a safer bet than 1996 -> 2016 Microsoft.
There's an argument they're not. Now obviously windows still dominates the laptop (and desktop) OS market (and I'm not gonna claim Microsoft is doing badly or anything), but it isn't the dominant overall OS due to the rise of mobile and Android.
At wave of computing so far, from mainframes to minicomputers, from minicomputers to PCs and from PCs to mobile, the dominant market leader has been unseated. If viewed in this light, Warren's reticence is prescient.
In '96 people were still talking about how Microsoft had failed to understand the importance of the internet, and whether Windows '95 would fix that. The '95 DOJ consent decree also looked set to potentially severely reign them in. Apple still looked like a possible contender.
OS/2 still looked like a possible contender - I remember being at trade shows at the time and seeing how hard OS/2 was pushed, at a time where Microsoft was still a small upstart that had only bypassed Commodore in revenues a few years prior (and speaking of Commodore, even in 95-97, several years after their bankruptcy, people were still looking at whether Escom and then Gateway would manage to resurrect Amiga), and there were lots of people convinced IBM would swat Microsoft away like a fly.
In the corporate space, options like DEC, Sun and SGI were still pushing into the workstation space at high pace and making inroads downwards into more regular workstations - I saw this first-hand in computer labs filled with cost reduced SGI Indy's and a bunch of DEC workstations at work, and lots of SUN workstations at places I contracted in those years.
Non-Windows, non-DOS machines were still everywhere in those years. It was unusual to find an office without a non-MS OS, because if nothing else there'd by a Mac for Quark Express or the like. And the presence of beachheads of non-MS OS's like that meant that whether or not MS could maintain its position was still not obvious.
More importantly: Giants had stumbled many times before. Most notably IBM, but the years before were littered with computer companies that had either died entirely or were shells of their former selves.
If you'd have said in 1997 that the most valuable companies in the world would include Google, Facebook and Amazon you'd have been laughed out of the room, when you then said that failing toy company apple would top the list
Even outside the world of IT, if you'd have told people in 1997 that a new car company would emerge and become one of the most valuable car companies in the world, given it had been 30 years since the previous car company had gone public, you'd have been equally mad.
In 1997 the most valuable companies in the world included Shell, Exxon, Toyota and Coca-Cola.
Predicting 20 years away is hard.
Sure you could have gone all-in on Amazon at IPO (ooh an online book cd sales company, with MP3s on the horizon), but you could easilly have gone all-in on Pets.com.
You could have invested in yahoo, after all that was the place that ran the web in the 90s - if you weren't on yahoo you didn't have a business. You could have piled into things like friends reunited, myspace, napster, all of which were just as likely to succeed as facebook, yahoo, or apple music.
Even dying companies like Blockbuster and Kodak took far longer to wipe out shareholder value than some new flash-in-the-pan companies.