NEW YORK ( TheStreet) -- I have no actual knowledge of the iPhone 5's details, but many people have asked me to provide my best estimate as to what the iPhone 5 will have and won't have. I am basing this article strictly on the logic of my own knowledge of the smartphone marketplace, including Apple's ( AAPL) public statements. I haven't talked to anybody at Apple or any of Apple's carrier partners about the iPhone 5.

Physical design: I believe Apple is likely to introduce a new physical design for the iPhone 5 that combines the design languages from the MacBook Air, the iPod Touch and the iPad 2. This would mean a return to the slightly rounded or beveled backside, perhaps chiseled somewhat in the vein of the MacBook Air. Unlike the iPhone 4's glass back, the iPhone 5 would have an all-metal design similar to the iPad 2.

Screen size: Most likely, it will be the same as the iPhone 4. Why mess with success? That said, Apple could try to push the boundaries on minimizing the bezel, causing the screen size to increase slightly, or for the device to become narrower. Either way, it would only be a matter of a millimeter or two.

Screen resolution: The same as the current one - 960 x 640; not a chance of any change here.

NFC: Until at least December 2010, I was convinced the iPhone 5 would make a huge deal about near-field communications. The public chatter in more recent months would lead us to believe that NFC is not going to be part of the iPhone 5. I still give it at least a 50-50 chance that Apple would at least include the NFC hardware in the iPhone 5, even if it wasn't yet ready to introduce any NFC software or services, such as iPay. After all, Research In Motion ( RIMM) will have NFC in every BlackBerry starting this August-September, and Google ( GOOG) will be pushing NFC hard before 2011 is over. Can Apple really afford to be behind here? Can iPay afford to wait?

LTE: This is really the big one. Apple dropped a hint at the Verizon ( VZ) press conference in January that it will be conservative with the implementation of LTE, primarily because of battery and other performance concerns. I believe the market realities are becoming such that it may be unwise for Apple to delay the introduction of LTE any more, in the face of 3 competitive smartphones on Verizon with LTE today ( Samsung, HTC and LG) and one more on the way by August ( Motorola ( MMI)). I guess it would be OK for Apple to introduce LTE perhaps as late as November 2011, but if the iPhone 5 hits the market by the end of September 2011, it implies that the iPhone 6 won't be available until June 2012 at the earliest, and that would create a dangerous bridge too far for Apple to attempt to cross. This is truly a 50-50.

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