It depends on the POD. If you mean only no coup of November 15th then it would only mean that the monarchy would probably cease to exist in 1891, after the death of Pedro II. By 1889 the monarchy had lost the support of the Church, the Army, the coffee landowners and most of the intelectuals (i.e, nearly everyone who matters, formers slaves and common people didn't have any influence in these affairs). Also, Isabel was disliked by most of these groups, and her French husband even more. There even some internal plots among politicians and members of the royal family to declare her nephew Pedro of Saxe-Coburg and Braganza as the new Emperor instead of her (and he was actively trying to replace her as the heir of his grandfather).
I really doubt that any late attempt to preserve the monarchy would work. If you want to keep the monarchy you need a POD as early as the Tripple Alliance War, or at least get rid of Isabel and find other heir. 1889 is too late for that.