Notably, there are very few operational LTE networks outside the United States. European mobile operators have been building out their HSPA+ networks over the past 12-18 months. Most of them have committed to using LTE for 4G, they're still a good 2-3 years away.The sim card slot is likely NOT for LTE, Apple wouldn’t jump on something that is not in use yet. Remember the first iPhone was EDGE and not 3G, even though 3G was already in use. Likely the sim card is because they have used the CDMA/GSM chip so the phone has global roaming capability since they are always trying to push the business aspect of the iPhone.
The logical progression for the iPhone would be HSPA+ support next, not LTE. I'm now thinking that we won't see an LTE iPhone until 2013.
I'm still of the belief that this iPhone 4 variant is for T-Mobile USA's network. That's the simplest explanation and I'm a firm believer in Occam's razor.