What will happen during the actual closure remains unclear but Foz de Iguacu in Brazil as an alternative airport remains the best bet
The dates seem to be more or less confirmed . 15th April for one month.
Salta will also close for three weeks after Easter but no exact dates as yet.
Here is the latest post from Sir Chandler ,, one of the most knowledgeable bloggers on Argentine aviation,
Sería algo complejo la operatoria por el cierre del aeropuerto de Iguazú