The updates to their Surface models including their ARM-based Windows RT version and Intel-powered Windows 8 edition will see the introduction of faster processors and higher-resolution screens and cameras.
Recently Microsoft wrote down $900m worth of first-generation RT stock that it could sell.
Analysts said demand for Microsoft's devices might continue to lag behind rival products.
However, they added that the firm's support for the product line was part of a long-term strategy that might ultimately pay off.
Windows-based tablets accounted for a 7% share of global shipments in the April-to-June quarter, according to a study by the tech advisory service Gartner.
By contrast, it said, Android-based tablets - including Samsung's Galaxy series, Android's Kindle Fires and Google's Nexus-branded range - had a 48% share, while Apple's iPads took 45% of the market.
The BBC said that despite poor sales for its Surface models - and a billion dollar write down - Microsoft is showing it is still determined to be in the tablet game.
It was the Surface RT model which was the real problem, apparently failing to find an audience, while the Surface Pro did relatively well in its (high) price bracket.
The problem is that most Microsoft users seem to have felt that the original Surface was not playful enough, yet too flimsy to be a work machine.
In a world of falling PC sales, changing their minds is now the company's major challenge.
Analysts claim that the outlook for the RT tablets is very low because consumers are still confused about what they are getting with the platform. "We aren't seeing a big uptake in the business market," said Roberta Cozza, a research director at Gartner.
"The 'pro' [Intel-based] range may do a bit better. The release of a new docking station and other accessories will help.
"But they're still quite pricey so it's unlikely to be a huge leap forward."
The upgrade also sees the RT version gain a 3.5 megapixel front camera and a 5MP rear one - making them both capable of capturing 1080p video.
The pro mode, however, retains the 720p-resolution camera found in its predecessor.
The Intel-based version does get Intel's fourth-generation Core i5 processor, which Microsoft said should help it attain 60% better battery life than the first model.