I'm wondering too.  Detroit 18 is probably my next amp if I can hold out long enough.  If I remember correctly Bruce said last October that Detroit was on hold "until sometime next year".  Which means sometime within the next 12-60 months...IF it sees the light of day.  Hell, it's only been 2 years since they demo'd that line at NAMM 2013.  That's nothing compared to the fabled E2...  
Still dying to play a Detroit 18 though...