Hmm, I think that, although the immediate cause(João Goulart) can be removed, a military coup would still happen some time later. There were too many people with too little regard for democracy(on both sides of the political divide) before 1964.
Also(and perhaps more importantly), you have the Brazilian military. Since 1889, whenever dissatisfaction with a government grew too much among those who mattered, the military stepped in and toppled the government. It had been so in 1889, 1930, 1945 and 1954(even though the last one wasn't a coup per se). Is it any wonder the military regarded itself as the stewards of the Republic, or that it decided the politicians were too incompetent to be trusted, and therefore military rule was the way to go?
As for Brazil being a first world nation today, had democracy continued past 1964, I don't believe so. In fact, a Brazil that hasn't experienced military rule for 20 would be quite similar to OTL's Brazil; the same economical ideas would have resulted in quite similar(or the same) economical plans, executed by people of the same background, if not the same people. Therefore, results should be quite similar.