"Given all the hoopla Microsoft has put around Office 365, they realize this needs to go off not just well but perfectly or Microsoft and Ballmer specifically will have another dent in its cloud story," Rebecca Wettemann, a Nucleus Research analyst, said via e-mail.

"From a cloud reputation perspective they really can't afford any hiccups here so it makes sense to nurture net new customers rather than more complex migrations from BPOS," she added.

Some industry observers have pointed out that implementing Office 365, and specifically migrating to it from BPOS, doesn't seem like a straightforward or simple process, especially when compared with implementations of similar suites built primarily for the cloud only like Google Apps.

A major selling point for Office 365 is its ability to interact and sync up with Microsoft desktop and server applications, letting organizations run a hybrid environment for communication and collaboration software that, in theory, provides the best of the on-premise and cloud worlds -- Microsoft's "software plus services" concept. But for this hybrid model to work in Office 365, the on-premise software has to meet new upgrade requirements.

This is because BPOS works with some older versions of on-premise software products that Office 365 can't connect to, so a migration may need to be preceded by an upgrade sweep of desktop and server software that customers have on premise.