Microsoft's Surface: What's next, what's needed?

With changes possibly set to be announced by Microsoft on Tuesday, it's a good chance to take stock of Microsoft's first full-fledged PC.

(Update: Microsoft announced the Surface Pro 3 on Tuesday.)

Does Microsoft need a smaller Windows RT 8.1-based tablet?

Mini mania passed: One obvious problem is that a Mini would be very late to the 7- and 8-inch tablet party. That fad has passed (even Apple's iPad Mini is now losing ground to its larger cousin, the iPad Air).

As tablet growth rates drop like a rock, momentum in corporate America is shifting toward larger "productivity" tablets and hybrids like the ThinkPad 10, Dell Venue Pro 11, and Samsung Galaxy Tab Pro 12.2. And don't forget that Apple is rumored to be working on a larger tablet for professionals.

So, would it be worth Microsoft's while to devote considerable resources to a small tablet, if the market is past its prime and the device is running the unpopular Windows RT operating system, to boot?

Only if Microsoft has something else planned that would expand RT's reach beyond the Universal Apps announced at the Build conference.

Pro 3? Microsoft has not redesigned the Surface Pro since the tablet debuted about a year and a half ago. A larger Surface pleases professionals and business customers who tend to like larger displays because it provides more real estate for the screen-intensive work they do.

And it would also provide a counter weight to an "iPad Pro" product that Apple may announce.

Other design changes? Let's face it, the Pro will never be the thinnest and lightest tablet around. Microsoft wants the Pro to be very fast (which it is) and so a svelte Sony Xperia Z2-like design probably isn't in the works.

That said, Microsoft could get the 2-pound tablet closer to the 1.6-pound Dell Venue 11 Pro. And, if Microsoft goes large (e.g., 12 inches), that would also necessitate a thinner design (it would be too heavy at the current thickness).

But Microsoft shouldn't alter the fundamental design too much, just improve it. Microsoft is ahead of tablet market leader Apple in the the hybrid tablet-laptop market (Apple doesn't have one).

Let's see if it can stay ahead.

Updated on May 20 at 3:00 p.m. PDT to reflect Surface Pro 3 announcement.

Updated at 8:30 p.m. PDT: Revises speculation about larger Surface Pro happening either Tuesday or later this year.