Just a few days ago, I've speculated about GSM 'virtually' surviving for quite some time in base stations which have radio and digital modules capable of handling several air interface technologies at the same time. Looks like Ericsson has also been thinking in this direction and has recently started a Work Item in 3GPP to explore Multi Standard Radios (MSR).
The main topic of this work item is to define physical layer characteristics when one transmitter sends out several carriers. So far, all characteristics like neighbor interference and blocking where defined around a single carrier. For Multi Standard Radios, the same definitions now have to be applied around all the carriers of one base station transmitter.
Good places to look for further info are GP-081607 which contains a nice figure on how a single radio module could handle GSM, UMTS and LTE together. GP-081608 is also quite interesting, again some figures and a list of frequency bands for which MSR should be explored first. As per this paper, Ericsson would like to explore Multi Standard Radios for UMTS and LTE for the 2.1 and 2.5 GHz band (band 1 and 7), and GSM, UMTS and LTE combined radios for the 850 MHz band (US, Canada) and 900 MHz (Europe, Asia) (band 5 and 8).
The Work Item description (RP-080758) lists Alcatel-Lucent, Huawei, Nokia Siemens Networks, NTT DoCoMo, TeliaSonera and T-Mobile as supporter, so E/// is far from alone.