The reason why the current Nexus 4 will not get LTE
First off I have the N4 and would love to have official LTE support. However I know why it will not happen for the model that is already on sale.
Basically to use LTE certain hardware the OEM has to pay standard essentiall parents to its inventors. These include Qualcomm, Nokia, Motorola and many others that i am not aware of. I am sure those add up to at least 40$ per unit. I know for a fact for example that t CDMA and 3G patents used to cost around 60$ per unit about 5 years ago, probably cheaper now, but LTE is a whole new and separate pool of patents.
So if LTE is to be supported officially Google will have to back-pay for those patents on all units sold. Every one who thinks this will happen is wrong, simply because the phone is sold at cost. The reason why LTE even works is because Qualcomm chips have the capability on the die, and cannot remove it. So if the OEM doesn't want LTE, they promise not to support it and therefore don't pay for it, even though it is physically on the phone.
Now if Google releases an LTE Nexus 4 it will be more expensive, probably 400$ starting price. The old models will never get the support for it from Google or anyone else. Its not because of T-Mobile or ATT or anyone else. It is because of the money Google would owe to Qualcomm for enabling. FCC certification would be the easy and cheap part of this.
I am writing this before I/O and I know of the rumors of LTE N4 so then i can say I knew it and can prove it.