Apple's big iPhone launch: What could go wrong

Apple's launch on Wednesday in San Francisco will kick off what analysts have repeatedly predicted was the biggest smartphone upgrade cycle in history. With those proclamations leading to what could be ridiculously high expectations, it's worth pondering the downside.

Now I'm not going to be dumb enough to doubt that Apple's iPhone 5 will outsell iPhone 4S by a wide margin. In fact, Apple's latest iPhone will launch with multiple carriers around the world. It's a global phone and distribution alone will ensure its success.

The wild card here will be the duration of this iPhone upgrade cycle. Meanwhile, there are other worries for the latest iPhone. Will these concerns materialize? Who knows, but it's certainly worth highlighting them amid the sea of gushing coverage on deck.

Let's play the contrarian game. Here's a look at the key wild cards surrounding the iPhone launch:

Carrier upgrade cycles. Apple got a healthy bump from the iPhone 4S launch. Those iPhone buyers in the U.S. are locked into two year contracts and few will pay heavy penalties to upgrade to the latest greatest Apple smartphone. Meanwhile, carriers won't allow customers to upgrade until they are 20 months into their contracts. That means that customers are locked into their old iPhones just a bit longer. As a result, Apple could see more steady demand over time as long as consumers don't decide after six months to wait around the iPhone 6.

Likely scenario: Apple will offset carrier upgrade cycles with new partners in global markets.

Consumer behavior. Apple is likely to get a massive bump from pent-up demand for the iPhone 5. The big question is what happens after all those new buyers go through the pipeline. Last quarter, it became clear that the iPhone upgrade cycle was getting shorter. After four months, it's quite possible that consumers will start waiting for the iPhone 6.

Likely scenario:Apple will see increasingly shorter iPhone demand cycles. That's why it needs a new hit---iPad Mini, iTV---to offset iPhone demand. Conversely, Apple could go for a faster release cycle, but that's difficult and may only make the upgrade progressions shorter. More: Why the iPhone 5 launch will be the "biggest upgrade in consumer electronics history"

The iPhone has already pounded the little sisters of the smartphone poor. NPD noted that Apple will have a tougher time taking share with the iPhone 5 largely because it has already beaten the likes of RIM and Nokia to a pulp. Samsung and Apple now run the smartphone landscape and both have feasted on a steady diet of RIM defectors.

Likely scenario: Apple's market share will increase a smidge vs. Android, but basically run in place. Profits trump market share anyway.

Perhaps the iPhone 5 isn't all that. According to numerous leaks there are two key features for the iPhone 5: The screen will be bigger and it will support 4G LTE. The catch is that Samsung has already been around with a larger screen and 4G devices. We'll let those two crazy smartphone makers yap in court about who is copying who. The iPhone will be a hit, but whether it lives up to Wall Street expectations remains to be seen. Trefis said in a research note:

The pent-up demand might mean a phenomenal holiday quarter for Apple, like last year, but it also puts its stock under the risk of the iPhone 5 not meeting customer expectations.

Likely scenario:Techies will be disappointed because most news about the iPhone already leaked. Keep in mind that the iPhone 4S looked very incremental too, but sold more units than previous version. More: Will the iPhone 5 display remain competitive?

Market saturation. In developed markets, smartphones are dominant. Most phones are now smart. In other words, there aren't a lot of easy wins for Apple or Samsung to exploit. Easy upgrades will be harder to come by. Keep in mind though that Apple's emerging market field is wide open. Apple is just now exploiting emerging markets. Should Apple somehow support China Mobile---a doubtful move given the carrier's proprietary network---these saturation concerns would disappear quickly.

Likely scenario:Apple gains won't come easy. As mentioned above, don't expect a massive share gain. More: Analyst: iPhone 5 sales could hit 10 million in first week

Related: CNET: Apple's Sept. 12 iPhone event: What to expect