Personally, I doubt that it will happen. Is current 2 x 77W daily regularly oversold and stuffed to the brim in loads? If not, swapping one of the 77W for a 388 may not make sense (and adding a 3rd daily even less so). Further, EK has already committed a lot of 388s to flights to/from UK: LHR, LGW and MAN (and potentially GLA, if rumours prove to be correct). Since BHX is roughly half way between LHR and MAN, those wishing to fly on a 388 have a choice. And reducing it down to a single 388 daily frame will probably not be a welcome development.

I see extra A380s being used either on single-frame/trunk routes like some to the US (or swapping it for one of the triple daily to JNB) or bringing it to more new destinations (like GLA and maybe GRU, once the runway is done).