1 Apache squadron for each of the strike corps is necessary at the minimum (16+). The Chinese also have 1 squadron-equivalent per GA (16), but that will very likely climb to match the American one (72-96 Apaches per corps).
I guess we are planning on equipping each of our corps with 1 squadron each as well. That would mean 4 Apache and 10 LCH squadrons. So 64-72 Apaches and 160-180 LCHs. Very doable. LCH numbers have to double again, 14 squadrons more.
Don't think there's an IMRH-based attack helicopter, but a new generation design. But that's a decade later. The IA has to start operating the Apache and LCH before they make requirements for a next gen design. Stealth, high speed, long range, large payload etc. The Americans are working on one.
The Bell Valor won their Black Hawk replacement program, and my money is on it winning the attack helicopter requirement as well.
It has more range than Rafale and more payload than LCA, can carry an M777 slung underneath. So we can't just make another Apache.