Research firm, IDC, has forecast that Microsoft's Windows 10 would fuel an increase in the company's share of the tablet market.
Almost all of Windows' growth over the next five years will come, not from pure slate-style tablets that mimic the iPad, but from 2-in-1 devices that combine elements of both tablets and laptops, IDC said. The vast majority of those devices will be purchased by businesses, not by consumers.
"A lot of the PC vendors, notably Acer and ASUS, are aggressive in the 2-in-1 space, and that's where the Windows tablet growth will come, from PC makers and 2-in-1s," said Jitesh Ubrani, an analyst with the researcher.
Microsoft's own Surface Pro 3 is one of the most visible, if not best-selling, 2-in-1; Microsoft markets the Surface Pro as a laptop replacement, even though that requires an optional $129 keyboard.
Unlike rival Gartner, which also regularly publishes device shipment forecasts, IDC counts 2-in-1s among tablets rather than lump them into the PC category.
According to IDC's latest estimate, OEMs (original equipment manufacturers) will ship 16.3 million Windows-powered tablets and 2-in-1s in 2015, a 41 per cent increase and enough to account for about 7% of the global tablet market of 235 million this year.
By 2019, IDC predicted, makers will ship 38 million Windows tablets and 2-in-1s, boosting the OS's share of the market to 14.1 per cent .
Meanwhile, iPad shipments will fall by 5 per cent this year, to 60.1 million from 2014's 63.4 million. During 2019, Apple will sell about the same number of iPads -- 61.9 million -- as it will this year.
Ubrani was less optimistic about Windows 10's ability to transform Microsoft's consumer slate-style tablet fortunes, although he acknowledged that the buzz around the upcoming OS upgrade -- which will probably hit retail on new devices this fall -- might bring some Microsoft loyalists back from rival Android and iOS platforms.
"I don't think that Windows 10 on slate tablets will play all that well in the consumer market," said Ubrani. "The action on Windows 10 will be almost all in 2-in-1s."
And the iPad? IDC believes its sales will be stuck at the 60-million mark, more or less, for the next five years, as far out as it pushes its forecasts. Even a long-rumored larger iPad -- one with a 12-in. display rather than the from-debut-standard 9.7-in. -- won't move the needle.
"A larger iPad probably won't add to the overall iPad market," said Ubrani, who saw little more than internal cannibalization by a 12-inch Apple tablet.
Others are also projecting a continued slumping of iPad sales when contrasted with 2014. Brian White of Cantor Fitzgerald, for instance, has iPad sales down 5% for the first quarter. His current model has Apple selling 61 million iPads in 2015.