Sorry, but no way will the current GTA continue in production without the facelift. You simply can't retool your high volume production line for a new model's revised bodyshell and panels (the most expensive part of the production process) then continue to run the old model - you'd have a massive double inventory requirement and duplication of lineside tooling etc which would make it completely unviable. Where Alfa have run old and new models concurently in the past, eg 105 Giulias alongside Alfettas from '72 to '76, they have been built on completely separate preduction lines.
They will either facelift the GTA along with the rest of the range (most likely) or they have built up stocks of the current one which they will sell out then drop it, which is unlikely, given the development costs they need to amortise and the high profile image of the GTA.
Selespeed Technology + Alfa build quality + alfa dealer competence + 2 years and 51K miles + Mental Instability = Another Sportwagon