I doubt EK or QR will be back at BHX for the foreseeable future, if at all. They rely on filling their planes with connecting pax. With borders all over the world closed or at best restricted for a long time to come, I just don't think they'll be able to fill a 380 or 777. Not saying nobody will be flying over the summer but there will be nowhere near the numbers to make it economical from anywhere except London.
Nobody can predict what is going to happen but if I was forced to make a prediction for BHX, I think the best we can hope for (making major assumptions that the virus has peaked and travel is permitted into Europe without too many restrictions and there is no second wave of infection here or abroad) is a small Jet2 programme, limited EI, FR and Wizz, limited LH/KL/AF and some domestics if LM, GR etc survive, others like LX, SK, may come back 2021.
If the virus cannot be bought under better control over the next month or two, maybe no flying at all from BHX and the vast majority of UK airports until the autumn?