Like a phoenix rising from the ashes, the idea that we’ve entered a “post-PC era" is about to make a huge comeback in 2015.

The signs are everywhere already, whether it's Microsoft’s (MSFT) Windows 10 introduction, IBM (IBM) highlighting its Apple (AAPL) iPad app efforts or Hewlett-Packard (HPQ) unveiling a new tablet line. Once Apple’s smart watch and rumored larger iPad arrive, the revival will be in full swing.

As the leading proponent of the post-PC mantra, Apple should also be one of the top beneficiaries. Sales of iPhones are already flying on the latest upgrade cycle but iPad sales have been a sore spot and likely declined for the first time last year. So CEO Tim Cook is expected to go bigger, with a more work-oriented tablet, and smaller, with a handy wrist communicator, this year.

Microsoft CEO Satya Nadella is moving quickly to sharpen and intensify his company’s focus on all the major post-PC trends, especially mobile and cloud computing. The Windows 10 introduction, while ostensibly highlighting the next iteration of the world’s most popular PC operating system, is just as much -- or more -- about winning future battles (even holographic ones).

A key feature of Windows 10 will be enhancing the ability of software developers to write programs that work across all Microsoft platforms, from PCs to phones and tablets to cloud servers. In theory, combining the huge audience of Windows PC users and the substantial share of Azure cloud computing users could make developers more likely to throw in support for the company’s minuscule base of mobile users.

Analysts are divided on whether the tactic will work. Among the challenges, people don’t use the same set of apps across mobile devices and PCs, notes Jan Dawson, chief analyst at Jackdaw Research. Few mobile developers will be motivated by the potential to reach PC users, he says.

Among the 50 most popular free apps on Android and iOS that are missing from Windows Phone, none have a Windows PC equivalent currently, meaning mobile developers don't see much appeal writing for PC users, Dawson wrote.

But some think Microsoft's mobile apps gap will become less important as cloud services rise to prominence. Windows 10 and other efforts are rightly blurring the boundaries between all kinds of platforms and devices with cloud offerings like the OneDrive storage service, Skype and even online versions of Office, says Bob O’Donnell, chief analyst at TECHanalysis Research.

If Microsoft gets more developers on its cloud platform, working across all kinds of devices, "then the whole 'app gap' problem in mobile starts to look a lot less concerning,” he writes.

Post-PC opportunities

At IBM, CEO Ginni Rometty skipped the company’s call with analysts, leaving CFO Martin Schroeter to deliver the bad news. Trying to change the subject, the CFO mentioned Apple seven times on the earnings call on Tuesday, matching the number of times executives mentioned IBM’s own homegrown supercomputer genius Watson. IBM agreed last year to write a series of iPad apps specifically for workers in industries like healthcare, finance and energy.

“We’ve seen strong customer interest,” Schroeter said in one of several discussions about the Apple deal. “This partnership is another example of how we’re helping enterprise clients to transform their business models and sources of value."

Big Blue, suffering from 11 consecutive quarters of declining revenue, is desperate to convince investors it can survive after PCs. The company last year dumped its server unit after getting rid of PC manufacturing a decade earlier, but even when it wasn’t making PCs, it was catering to corporations filled with PC users. Now even that last bastion is looking to cloud and mobile platforms, prompting IBM’s latest shifts.

Last year HP and CEO Meg Whitman were huge beneficiaries of the PC’s resurgence. Sales in HP's personal computers unit rose 7% for the year ended Oct. 31, 2014, after dropping 7% the year before and 10% in 2012. A big portion of those sales were companies upgrading ancient PCs running Windows XP, a trend that’s likely run its course. So now comes Whitman's new slate of tablets, running Windows and Google (GOOGL) Android software. She's also emphasized 3D printing, cloud computing and other post-PC initiatives.

And all this activity is nothing compared to what is likely to happen when Apple goes bigger with a new iPad. Rumors have been swirling over the past year, but this week KGI Securities analyst Ming-Chi Kuo added new details and predicted a second-quarter arrival date.

Samsung (005930.KS) and others have already gone beyond the 10-inch screen size with tablets, and Microsoft’s latest Surface Pro 3 line has a 12-inch screen. But many companies had tablets before Apple’s 2010 iPad arrived and the iPad still took the world by storm. Expect more of the same when Apple's latest innovation hits.

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