Multinational projects are always liable to fail. The MRCA was a success, and the German, Italian and British Air Forces got an advanced strike aircraft that the RAF turned into a long Range interceptor. But what would have happened if the MRCA had gone the way of the MBT70?
Would the Air Forces involved have bought other aircraft? Updated old ones? Would the Eurofighter project been killed?
Would the Mirage 4000 been an option?
Here a possible outcome:
The Germans eventualy replace their F104G and F4F with F15E
The RAF upgrades the Bucc and the Lightning, buys more used Phantoms, and develops a British Typhoon at an erlier date.
The Italians build more AMX and buy F16s
The Eurofighter is stillborn
The Mirage 4000 still fails