Ever since it completed the acquisition of Nokia's Devices and Services unit, Microsoft has been constantly looking into ways to expand its phone lineup, and it appears that we're not very far from three completely new models launching under the Microsoft Lumia brand.

While Lumia 535 was the very first device to adopt this brand, it appears that Microsoft is working at full speed to bring more such phones to the market, and three of these models have recently been spotted online by ad companies.

AdDuplex has revealed in a very short tweet today that “at least 3 new phones with Microsoft as manufacturer” have appeared in logs, adding that these devices have displays ranging between 4 and 5.7 inches.

No other details have been provided for the moment, but there's no doubt that Microsoft is indeed working to expand its Lumia lineup with new models, so more information should emerge soon.

An entry level and a flagship

Even though details are so vague right now, those screen sizes actually tell us a lot about Microsoft's short-term plans for the mobile industry.

A 4-inch device would clearly be aimed at emerging markets, where the price is the number one factor for a successful phone. There's no doubt that a 4-inch Windows Phone handset, which could be available for about 100 dollars (73 euros) or even less, would appeal to many Android buyers looking for affordable phones, and that's exactly what Microsoft hopes to get with these models.

Such a device would fit perfectly in Microsoft's plans for countries such as China and India but could also be launched in other strong markets if there's demand.

On the other hand, a 5.7-inch Windows Phone device would be a completely new model for Microsoft and would be specifically aimed at those looking for a flagship running its own smartphone operating system.

At this point, Microsoft has absolutely no phone between 5 inches (Lumia 930) and 6 inches (Lumia 1520), so the new 5.7-inch device would try to fill in a gap that pushes Microsoft out of a more direct battle with phones such as the Samsung Galaxy Note 4.

The 5.7-inch Windows Phone model could also be a successor to the Lumia 1520, a phablet that has already been sold very well, but which has received some criticism because of its size. Reducing its overall dimensions could help Microsoft boost sales, but it also depends on the overall performance of the new OS powering the device.

Windows Phone 10 is also expected to launch next year, so these new devices could actually be the first Microsoft Lumia-branded phones to come with the new smartphone platform.