Yes I understand what you mean. But what I mean city might lose both clients and they might lose all the events aswell as it would probably cost too much to maintain it.
Scenario A: both clubs go elsewhere -> Meazza won't be maintained as city cannot afford it, also loses all possible money from events (though no idea is this a relevant sum)
Scenario B: Inter stays -> city gives a nice deal to Inter but they get to keep Meazza running
I think with Scenario B is that the actual renovation which would suit Inter would cost too much but maybe if Inter would become part owner of the stadium or some similar arrangement, it could be agreed to do better renovation than what the city would do my themselves.
But as said, pure speculation by me since I don't have any credible numbers for either scenario.