LTE iPad 3 is not for sure. Here's why...
There are quite a few people certain that the iPad 3 will have LTE. I'm not so sure.
First off, here is a list of current Apple products and their baseband chipsets: (sorted chronologically)
- iPhone 3GS - Infineon 337S3754 (GSM)
- iPad - Infineon 337S3754 (GSM)
- iPhone 4 - Qualcomm MDM6600 (CDMA) or Infineon 337S3833 (GSM)
- iPad 2 - Qualcomm MDM6600 (CDMA) or Infineon 337S3833 (GSM)
- iPhone 4S - Qualcomm MDM6610 (CDMA & GSM)
It's pretty obvious from above that Apple likes to share chipsets among it's products. The iPhone 3GS and the iPad have the same baseband chipset. The iPhone 4 and iPad 2 share the same baseband chipset. It's also worth noting that the MDM6610 is a minor update to the MDM6600. I tried to look for differences, but I was unable to find any.
The reason there is not LTE in the iPhone 4S is perfectly described here by Anand Shimpi. It boils down to the fact that in order to get LTE on the iPhone, it would need another chip on the PCB. Qualcomm has a new chip entering production in Q2 2012 that will solve this problem. It will be called the MDM9615.
If the iPad 3 has LTE, it will have the MDM6610 for 3G and the MDM9600 (a data only chip) for LTE. As mentioned earlier, Apple did not do this on the iPhone 4S due to size and battery constraints.
I wouldn't be surprised if the iPad announced next week is the iPad HD with the MDM6610 only. Then in October, they could release the iPhone LTE and iPad LTE with the MDM9615.
tl;dr: I would bet that the next iPad doesn't have LTE, but I wouldn't be surprised either way.