Tuesday Microsoft released a Zune software update that some Microsoft watchers are interpreting as evidence of the impending arrival of a new type of phone with Zune functionality, perhaps the long rumored ‘Pink’ smartphone.

As stated by Microsoft blogger Long Zheng, the latest Zune update contains code for three new hardware identifiers and three new Product IDs (PID) that are distinct from the existing ones for Zune devices. These could represent the addition of support for three actual hardware SKUs, according to Zheng.

“What might seem like a simple update regular software hides in reality a very important secret. The ‘ Zune Phone ‘ is almost confirmed,” Zheng wrote in one post.

Although this could be a sign of a coming integration of Zune software into Windows Mobile 7, Zheng noted that references identifiers of hardware drivers that are locked to Microsoft, and as such can be hidden without violating regulations of USB body.

Given the thick blanket of secrecy around Microsoft’s Windows Mobile 7 plans, this is definitely plausible. Microsoft has recently begun to hint that it will share some new kind of mobile linked to the next Mobile World Congress and MIX10 conference. But company executives haven’t uttered the words ‘Windows Mobile 7′ in months, instead preferring to maintain an Apple-esque silence when face with questions about Microsoft’s foundering mobile strategy.

Does Zheng’s discovery portend the arrival of the long rumored Pink? That project, in which Microsoft has reportedly been working with Sharp, maker of the Sidekick, develop a smartphone with music, games and social networking features, has been rumored to be on the rocks last October. But Pink is actually still alive, a source familiar with the project told Channelweb.com this week.

According to the source, which originally Channelweb.com briefed on the case last May, Pink has suffered from mismanagement and repeated delays that have plagued the Windows Mobile 7. Microsoft is still forging ahead with Pink, but Microsoft’s Premium Mobile Experiences (PMX) division, which is leading development of Pink, has reduced the number of the most compelling features, the source said.

Microsoft has something up its sleeve, but given the many areas where its mobile strategy needs fixing, it is any one’s guess whether the forthcoming revelations will help make up for the ground it has lost in the hard charging mobile market. For that to happen, it will have to be something big.