Telstra (mobile operator in Australia) plan to shut down their GSM network in 13 months time - December 2016. Optus (Australia) confirmed they are shutting down their GSM network in 17 months time - April 2017. We already have iSocket in the 3G version, which is undergoing the certification process for Australia now. We plan to announce pre-ordering for the Australian model soon. We are also working on an exchange program for current owners of GSM products.
The American version of iSocket 3G (for T-Mobile and AT&T networks) is already available for pre-preordering with anticipated shipping in January 2016. iSocket 3G for the other countries, where operators are not yet shutting down GSM networks, will be available ex-stock in the next year.
Why not 4G or 5G? In short: to keep costs to a minimum. For more information, please see this post.