Ever since Apple launched the iPad, the storyline of Microsoft's (NASDAQ:MSFT) Office for iPad has been impossible to bury. Even so, it has been four years since Steve Jobs unveiled Apple's tablet and Microsoft's dominant productivity suite still hasn't made it to iOS. But with productivity software competitors gaining traction in mobile, Microsoft finally appears to be ready to launch a version of Office for iPad.

Shares jumped about 4% on Tuesday when Reuters reported that new Microsoft CEO Satya Nadella would unveil Office for iPad on March 27. Judging by the rally in Microsoft's stock price that has sent shares to levels not reached since the dot.com boom in 2000, it is pretty clear that investors are excited about the software -- and for good reason.

Waiting is no longer an option
There are various estimates of just how much money Microsoft is losing by not having a version of Office for the iPad. While the estimates differ, they all seem to suggest that Microsoft is missing out on a significant opportunity.

One comes from Morgan Stanley analyst Adam Holt, who estimates that if the suite is priced at $60 for an annual subscription, about 30% of iPad users would buy the software. The end result? Apple could generate a whopping $2.5 billion in revenue annually -- and that's after the 30% App Store commission. Based on his claim that 30%-40% of Mac users install Office on their Apple computers, a 30% installation rate among iPad users sounds reasonable.

Taking Holt's estimate further, assuming 35% of this revenue hits the bottom line, Office for iPad could grow Microsoft's annual net income by about 4%. That's a significant gain for a cash cow like Microsoft.

But the move to launch Office for iPad would have significant intangible benefits, too. Particularly, it would give Office a competitive position in a space where productivity suite competitors are mounting. Both Google and Apple now offer versions of their productivity software for free. And beyond the big tech giants, there are hundreds of other productivity software alternatives in the App Store.

Microsoft Office for Mac. Source: Microsoft.

Further, Microsoft's launch of Office for iPad could send the long-awaited signal to investors that it is ready to take on a cross-platform approach. A recent comment from Microsoft's Thorsten Hubschen, who oversees Office in Germany, that the company is renewing its Office for Mac efforts also supports the idea that Microsoft is headed toward a cross-platform strategy.

A change of direction?
For Microsoft investors, a launch of a version of the productivity software for the world's most popular tablet should provide incremental confidence in the company's ability to shift its products to a mobile-dominated future. Further, the launch of Office for iPad signals that Microsoft is finally ready to make the important shift to a cross-platform software environment -- an imperative move that best happens sooner than later.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.