You may have noticed the piece by Harlin McEwen, Chair of FirstNet's Public Safety Advisory Committee (PSAC), in Urgent Communications on his thoughts about LTE replacing Public Safety Mission Critical voice.
The consensus among experts has been that it will be years before LTE can replace Public Safety Mission Critical land mobile radio, however the timelines being discussed range anywhere from 3 to 20 years.
Although Mission Critical voice standards have been incorporated into LTE standards in preparation for such an endeavour, traditionally, commercial systems have been unable to support direct-mode talk-around.
In the article, McEwen maintains that the experts who say that it is not yet time for this transition are not driven by the Land Mobile Radio (LMR) industry, but by the trends of the past and the facts of the present.
According to McEwen, new communications tools usually supplement their predecessors, being used side by side (often indefinitely) rather than fully replacing them, and McEwen does not give a timeline, however he agrees with the National Public Safety Telecommunications Council (NPSTC) statement that "Local, tribal, state, and federal public officials are urged to not abandon or stop funding their public-safety voice LMR systems until such time as it can be demonstrated that broadband can safely and adequately provide public safety with mission-critical requirements currently provided by LMR."
In other words, we shouldn't be holding our breath, or making any plans to make such a transition in the conceivable future, but it is just over the next horizon.