When it comes to Apple, hope and pessimism spring eternal. Just ask the accidentally dueling billionaires Carl Icahn and Larry Ellison.

Oracle co-founder and CEO Ellison, in a interview with Charlie Rose that aired on "CBS This Morning" last Tuesday, predicted that, as the Los Angeles Times summed up in a headline, "Apple is doomed without Steve Jobs." He conveyed his feelings in a sort of real-time infographic: "We saw Apple with Steve Jobs," Ellison said while raising his finger. "Now, we're gonna see Apple without Steve Jobs," he added while dropping his finger.

Later that same day, perhaps not coincidentally, mega investor Carl Icahn (aka the most notorious corporate raider of the '80s), conveyed his opinion just as succinctly. "We currently have a large position in APPLE," he tweeted. "We believe the company to be extremely undervalued. Spoke to Tim Cook today. More to come."

With that, he goosed AAPL stock nearly 5%, adding $17 billion in market cap to the company by the end of the trading day.

Which billionaire should you side with? That depends on how you feel about Apple's ability to continue to innovate -- i.e., is an Apple "smartwatch" really imminent? -- and where you think its existing products will fit in a rapidly morphing marketplace.

On the one hand, as my colleague John McDermott reported last month, Apple set a record for its June quarter, selling 31.2 million iPhones, vs. 26 million in the same quarter last year. Investors welcomed that news, but it's worth noting that Apple's revenue-per-phone has been dropping -- to $581 per unit in the June quarter vs. $608 in the same quarter last year. (Consumers in the U.S., of course, typically pay only a fraction of those prices because carriers pay the balance of the real cost of iPhones as a contract-signing inducement.)

Now consider that last week research firm Gartner announced that smartphones outsold feature phones worldwide for the first time during the April-to-June quarter. In other words, we've reached a tipping point and now smartphones are becoming almost commoditized. And along the way, Apple's position as the maker of the definitive smartphone eroded. Per Gartner, Apple's global smartphone market share dropped to 14.2% from 18.8% in the same quarter last year. (Samsung currently leads with 31.7% market share.)

But Apple seems poised to introduce a more competitive set of iPhones -- including, possibly, a more affordable "emerging market" model -- so let's move on to Apple's other marquee product, the iPad.

There the news is really grim: iPad sales dropped to 14.6 million units during the June quarter, vs. 17 million during the same quarter last year. (Mac sales -- oh, right, Apple still makes desktop and laptop computers -- were also down, from 4 million to 3.8 million.)

Various industry observers have put forward explanations (e.g., channel inventory, the lack of a new big-screen iPad model), but what I find alarming is the fact that last November's introduction of the more affordable, more portable iPad Mini didn't mitigate the iPad's overall sales decline.

I've got friends and colleagues who continue to adore their iPads and who would find the idea that iPad sales are sinking -- that the iPad has possibly already peaked -- to be mystifying.

Then again, my friends and colleagues and I mostly live in certain sorts of bubbles -- media bubbles, socioeconomic bubbles (middle-class and up), etc. -- and we tend to have lifestyles in which owning an expensive, dedicated media-consumption device makes sense.

But look around at the real world -- the rest of the real world, I mean -- and you'll understand why high-margin-loving Apple is increasingly finding it hard to compete in a category it basically created. Because $499 and up for the iPad, or $329 and up for the iPad Mini, is just too damn expensive. Meanwhile, Apple's competitors are getting really good, really fast, at creating cheaper, better iPad alternatives.

But, heck, in certain -- arguably most -- socioeconomic circles, paying even $239 for Google's just-released, excellent Nexus 7 ($100 less than the iPad Mini it competes with) is still probably too much for a dedicated media-consumption device. Especially when you consider how many millions of people are more than comfortable enough already, thank you very much, consuming media on the increasingly awesome, ultra-portable, pocketable, multipurpose devices they carry with them absolutely everywhere: their smartphones.

And with the rise of big-screen smartphones, well, remind me again why I need an iPad Mini or, erm, an iPad Maxi ... or any kind of tablet, for that matter?

Earlier this month, Bloomberg News reported that "Global tablet shipments slowed in the second quarter from the previous three months" -- unit sales declined 9.7% to 45.1 million -- "as consumers delayed purchases of Apple's iPad to wait for a new model expected later this year, according to researcher IDC." OK, sure, that's one explanation.

Another explanation, a scary one, is that maybe the tablet market is way niche-ier than we in the tech, media and marketing worlds thought it would be. And the iPad is becoming the high-end niche within a niche that big-screen smartphones are cannibalizing.

How small could that niche-within-a-niche get? Stay tuned.

Simon Dumenco is the "Media Guy" columnist for Advertising Age. You can follow him on Twitter @simondumenco.