Apple (NASDAQ:AAPL) is widely expected to unveil a larger tablet, the iPad Pro, at some point this year. Several of its competitors, including Samsung (NASDAQOTH: SSNLF), Microsoft (NASDAQ:MSFT), and Hewlett-Packard, have already launched larger tablets of their own, making the prospect of a 12- or 13-inch iPad unsurprising.

iPad sales have begun to wane in recent quarters, falling short of analyst expectations and challenging the long-standing notion that the iPad would eventually become Apple's largest business. Apple's management insists the iPad's current problems are a temporary speed bump, but something more is clearly needed.

The last time Apple launched an iPad with a different screen size -- the iPad Mini in 2012 -- shipments of its tablets subsequently surged. Would a larger iPad produce a similar result?

Large tablets haven't exactly set the world on fire
Simply put: Probably not. Unlike the iPad Mini, it's not particularly clear that there's a high demand for a large iPad.

In Sept., 2011, Amazon unveiled the original Kindle Fire tablet -- a 7-inch, $199 tablet that ultimately sold millions and inspired dozens of similar Android-powered devices. With small Android tablets carving out a large (and growing) niche, Apple was forced to respond -- and it did, with the iPad Mini. At $329, it was far more affordable than the full-size iPad, and it quickly overtook its larger sibling to become the best-selling model.

It would be quite a shock if a larger iPad produced a similar effect. Samsung hasn't released exact sales figures for its large tablets -- the 12.2-inch Galaxy Note Pro and Galaxy Tab Pro -- but Digitimes Research estimated last year that annual sales would fall short of 1 million units. That's a drop in the bucket compared to sales of Apple's iPad, which exceeded 12 million units just last quarter.

Microsoft markets its Surface Pro 3 as a laptop alternative rather than a tablet -- and it is, running the full version of Microsoft's Windows 8.1 operating system. But with a full touch screen and detachable keyboard, the Surface Pro 3 is just as much of a tablet as it is a laptop, and with its 12-inch screen, it's a large tablet at that.

Microsoft said its Surface sales doubled last quarter, with revenue rising to $400 million. It's clear there's a market for the Surface Pro 3, but with an average selling price close to $1,000, annual unit sales are running in the low single-digit millions, at best.

Of course, Apple isn't Samsung or Microsoft, but a large iPad would likely suffer from the same issues, especially on pricing. A large iPad is virtually guaranteed to be more expensive than the iPad Air, making it a tough sell to consumers.

The struggling iPad
Still, it may not be a bad product for the company on a strategic basis. Apple's partnership with IBM has already led to the creation of several enterprise-focused iOS apps -- a large iPad could become the preferred mobile device of business users. Over time, those customers may be more reliable and less willing to be swayed by cheaper competition.

But in the short-term, a large iPad doesn't appear to be savior the iPad needs. Last quarter, iPad sales fell 13% on an annual basis, continuing a trend that has seen the iPad miss sales estimates for more than a year. To be clear, the iPad is still generating billions, but it's no longer Apple's second-largest business.

The iPad Pro should attract attention and could fill an important niche, but unless it can offer something truly compelling, it's unlikely to be a big seller.