Although Bethesda has never outright confirmed that an Elder Scrolls MMO is being created, Fudzilla reports that as many as 100 people have been working on it since 2006 – or around the time TES IV: Oblivion launched. Bethesda has supposedly continuously funded that project, but the number of people laboring on it has fluctuated over the years.
As for the possibility of a cookie-cutter offline TES title, an Elder Scrolls V novel was released and described as "[partly bridging] the gap for the next game, which is set 200 years after the Oblivion crisis." This leaves us with nothing but speculation, but June 15 will be here in no time. Until then, let your imagination run wild.