(Pocket-lint) - Greg Sullivan, senior product manager of Windows Phone, has told Pocket-lint that Microsoft is very much working on upgrades to the Windows Phone operating system, but is changing tactics in how it goes about letting us know about it.

In a candid chat with Pocket-lint over a coffee in a café at Mobile World Congress, Sullivan discussed a number of things about the Windows Phone operating system, telling us that the OS is really starting to build momentum,.

It's something that Stephen Elop, CEO of Nokia, also confirmed to us in an earlier interview at the show.

According to Sullivan three times as many people as last year are walking into stores to ask for a Windows Phone device, and four times as many people are walking out with one.

It is that momentum, helped partly by low-cost devices performing well against the direct competition, that Microsoft doesn't want to upset, and so rather than follow 2012's schedule of announcing the next software iteration of Windows Phone at Mobile World Congress, the company is holding back.

"We are taking a different approach on the announcements this year," confirmed Sullivan.

It seems this time it's more about working behind the scenes, rather than announcing that new details are coming, waiting six months to detail it further, then waiting a further five months before releasing devices to consumers.

"It is safe to assume we are working on low and high-end devices, but at the moment there are a lot of meetings going on with partners behind the scenes," said Sullivan.

That tallies with other comments made to other reporters at MWC.

"We're going to have an upgrade path going forward. Windows Phone 8 can evolve. We have an architecture that enables portability and is fundamentally hardware independent," said Sullivan. "As the market evolves and customer requirements demand it, we'll evaluate options."

That behind the scenes approach seems to be in full effect, more so than many perhaps have realised until now.

Microsoft, absent from CES earlier in the year, was also not in evidence on the show floor in Barcelona. There was no big press conference, and rather than opt for a hotel directly opposite the trade show as it has in previous years, the company held its meetings in a hotel 20 minutes from the venue.

While the hotel might have been covered in Microsoft billboards, once inside it was decidedly low key, with Pocket-lint conduct also interviews with other members of the Microsoft team there.

But as our meeting point illustrated - a coffee in a busy café - this is Microsoft working the back channel, in stealth mode so to speak.

The tactic is a decided step change from previous years, but one that Windows Phone probably needs if partners like Nokia, which appears to be dominating the Windows Phone market, are to have any chance of selling phones to consumers before wind of the next bigger, better device gets out - something that is already starting to happen.

Last year the announcement that the current line-up of devices such as the Lumia 900 would not be getting the full update hampered sales, and although Microsoft has said that any future upgrades wouldn't encounter the same problems, it's clearly something it wants to avoid.

Talking to several Microsoft employees and partners across the week, on and off the record, it seems Microsoft is very busy detailing the virtues of what's next, but for the time being only to a handful of people.

Expect new features, toys, and devices in the coming months.

Writing by Stuart Miles.