But by adding iOS and Android, Microsoft would make it much more likely that Office 365 customers could, in fact, equip more than three devices with the suite. Those two operating systems own the lion's share of the smartphone and tablet markets. Because Windows-based devices have minuscule market shares, the inclusion of iOS and Android could also help Office 365 gain traction until Windows RT and Windows Phone 8 grow their shares.
And if Office Mobile does require Office 365 -- if the apps aren't available for purchase separately -- Microsoft creates a huge incentive for users to subscribe, not only boosting sales but also attracting customers who otherwise might never have considered the rental model or even the new Office.
Ullman was optimistic that consumers would, if not in the short term, then in the long, shift to the Office 365 model.
"It's how consumers are consuming software now," he argued. "They're used to paying a subscription license, especially younger consumers, and they're moving away from paying up front for a perpetual license. They're using software, and if it doesn't work for them, they move to something new. I see [Office 365] as Microsoft's way of being part of this."
Ullman was adamant that the rental model was attractive to younger users. "The whole concept of upgrading is foreign to them," said Ullman. "Younger users don't even know what an upgrade is, since most of their software is updated all the time."
Consumers are, however, a small part of Microsoft's Office business, which last quarter brought in over $5 billion in revenue, or more than 34% of the company's total for the period. Microsoft makes most of that not from sales of Office to consumers, but on sales and volume licensing contracts to enterprises.
Linking iOS and Android Office apps to Office 365 also is a smart move for Microsoft in the enterprise, Ullman said, what with businesses shifting to a "bring-your-own-device" (BYOD) concept, where employees decide what hardware they'll use for work.
"Companies are adapting to younger workers -- as well as those in the C-level suites -- coming into the workforce with their own devices," Ullman said. "And Microsoft must adapt their licensing to that."
As Ullman sees it, Microsoft has two options with iOS and Android Office apps. It can either link the apps with Office 365, or add "usage rights" to the mobile software as part of Software Assurance.
The former would "push Office 365 into the enterprise as a licensing solution," said Ullman, while the latter would "be a way of keeping customers on Software Assurance."
Either would be what he called a "smart move," but Ullman wasn't ready to bet on one over the other. "I'm not sure which way they'll go," he said.