I think AI will be taking delivery in October as they had said long time ago. You might have already seen VT-ANA at the Boeing factory, already painted in AI colours.
They will probably take a part of the 27 aircraft in October and the remaining later on. Perhaps 10 now, rest later.. or in similar installments.
The 787s cannot replace the 777s. They are two different categories of aircraft. The 787 is medium haul and the 777 is long range. Ofcourse, AI with its infamous mismanagement, uses an LR 777 for ridiculous flights like BOM-AHD and BOM-DEL and many more! No wonder AI loses money.