Why are you saying it's better to convert the licenses before the World Cup?
Because anyone who does so will have a head start IF foreign pilots are allowed to fly here in the future.
I said before the World Cup because IF the law is going to change that will most likely be the moment it does so, when the government realises that any rapid expansion can't be covered by the training schools here and they need to bring in foreigners.
You know what Brazil is like, everything done at the last moment. Any candidate who can cut a month or two off the recruitment process will have an advantage, and will have demonstrated a level of commitment to flying in Brazil that sets them apart.
Of course the above might not happen, and converting licences might be a complete waste of time and money, but with the investment most pilots have already made to pursue their chosen career, this is a relatively low cost option that could make all the difference.
To be perfectly clear, this is my personal opinion based on living and working here for 10 years, so feel free to disagree with what I've said.
TTFN