It is important to note that Brazilian economy's minister said there is no plan to implement a common currency[0].

This declaration came after Argentinian ambassor said, in a visit to Brazil, that there were plans to create it.

It seems to me that this is something that Argentina wants, while Brazil has no practical interest in it.

Worth mentioning that Argentina is a country that is dealing with deep financial crisis and heavy inflation and a common currency could help to reduce inflation. Brazil had similar problems through the 80's and 90's.

[0] - portuguese: https://www.cnnbrasil.com.br/business/nao-existe-proposta-de...