The Brazilian National team right now is a total mess and in little over 1 year there will be the World Cup: I really struggle to image Ancelotti accepting this type of offer while having only one year to prepare Brazil for the World Cup. If he actually manages Brazil will be after the World Cup, not before, there are just too many risks otherwise.
This rumours have been circulating from a year or so. First it was denied since things went very well with Real Madrid. This season was different and with the struggle of the team to stay stable and the knockout they got in UEFA Champions League then this possibility remains high. Carlo Ancelotti might join the Brazilian national team indeed because after all he already knows directly or indirectly some players there so he will not totally start from the ground. In fact this will help him fix the team faster.
I personally see it as an opportunity to revive Brazil and be a hero.