With Apple WWDC kicking off June 10, speculation is ramping up regarding what products Apple will unveil at the conference. The iPad mini 2, iPhone 6 and iPhone 5S are all possibilities, but what's most likely at this point?

We reported earlier that the iPhone 6 was recently spotted in the UK on a Vodafone inventory list. While nothing's been confirmed yet, the possibly imminent release of the iPhone 6 raises an interesting question: what happened to the iPhone 5S?

With the exception of the first iPhone, Apple has released an "S" version for every iteration, beginning with the iPhone 3GS. Cupertino, like usual, has remained mum on the subject, and has yet to indicate if an iPhone 5S will precede the iPhone 6, or if an iPhone 6 is even in the pipeline.  

iPhone 6 vs. iPhone 5S: What does Apple need more?

A salient question to ask right now is whether Apple needs a one-run homer or a grand slam in the next product cycle. While the company has had great success with its incremental "S" version updates, the market is somewhat different than it was when the iPhone 5 came out.

Flagship smartphones from just about every major developer have debuted since the iPhone 5 rolled out, including the Samsung Galaxy S4, HTC One and BlackBerry Z10. In addition, the iPhone's competitors have never been as widely available before and offered at such an attractive price point. Most of the new smartphones are available across the Big Four telecoms and most cost less money.

If Apple was ever going to skip an "S" version iPhone in favor of rolling out a brand new device, now is the time. Although they've started to pick up again, shares of Apple have been dropping steadily for awhile now and an iPhone 6 release may be what the company needs to reclaim its spot as world's most valuable company.