This might sound unusual though this is what Asus Germany has said they are up to. The revelation was made in the German FaceBook page for Asus wherein in response to a query as to whether an UMTS Transformer Prime will be the next to hit shelves — that is after its Wi-Fi version has done in January — Asus stated they are not into anything of that sort. As for reason, Asus cited low demand for such a version of the Transformer Prime.
“This time there will be no model with UMTS. We want to emphasize that we are aware of the strong demand for UMTS models in Germany and would like to serve. However, in many other countries’ UMTS networks are not so common and so the worldwide sales volumes for UMTS models are not particularly large. Furthermore, most UMTS pads are sold in Germany through the Telco channel and there are 1 EUR especially subsidized products requires a contract, the price point may not make an Eee Pad Transformer Prime unfortunately” ASUS Germany (translated)
Asus believes a Transformer Prime with integrated UTMS modem will be priced prohibitively high which might not have enough takers if carriers are not willing to subsidize it accordingly.
However, those in the US might still be offered a LTE or CDMA version of the Asus quad core tablet though here too, its mere speculation.