I guess the individual mandate would be deemed unconstitutional, and the president would not be able to enforce it, in districts covered by the federal judicial circuit whose Court of Appeals ruled it unconstitutional, since such decision would stand; but the individual mandate would be enforceable in the circuit whose Court of Appeals ruled it constitutional. And as for other circuits, they could do whatever they wanted.
A rational president would realize that having an entire federal judicial circuit in which the individual mandate could not be enforced would cause the entire scheme to unravel, and would move to adopt a new healthcare scheme, just as he would had the Supreme Court struck it down, but we’re not dealing with a rational president.
In any event, we need to get 5 Justices to declare the individual mandate unconstitutional, and elect a Congress and a president who will repeal the entire law.
There is no severability clause in the legislation, so if the individual mandate is deemed unconstitutional, the judges could declare the entire law unconstitutional making repeal unnecessary. SCOTUS will have to address that in their decision.