The hub business will certainly go on, some will gain in importance and some will reduce as new travel patterns emerge. Addis would be the natural one for Africa, Singapore for SE Asia, London for Europe to North America etc. Turkey is very well positioned between Europe and Asia, and Turkish Airlines fly to more destinations than any other.
A single location may be unable to support three mega carriers all chasing the same market, an EK/EY merger would make sense, even just code sharing and coordinating schedules would go a long way.
Survival over the next few years will depend on who has the deepest pockets and gets the most support.