In the Bosnian constitutional framework set by the Dayton Agreement (1995), Republika Srpska cannot achieve independence without the consent of the Bosnian federal authorities in Sarajevo, which are of course hostile to the loss of 49% of the territory of the federation. An amicable separation is hence unlikely.
In International Law, it's more ambiguous.. and paradoxal, because the "de facto" primes on the "de jure". The principle of self-determination enshrined in the UN Charter competes with the principle of States cooptation for any entry of a new Member in the United Nations : because the International Law is upheld by its subjects themselves and not by an "International State", its "de jure" nature conflicts with its "de facto" organization & modus operandi.
So if we speak about self-determination, and that we add the 3 characters of a State already "owned" by Republika Srpska (a territory, a population, an administration with a very high degree of autonomy controlling that territory and that population), then substract the fact that Republika Srpska bent to pressure and surrendered its armed forces to the Bosnian Federation in 2005-2006, and more importantly, the fact that the NATO patrons of the Bosnian federation are hostile to the independence of Republika Srpska, we have a case in which RS's independence is possible, but is at the same time improbable.
On the other hand, the case of Kosovo directly mirrors the case of Republika Srpska : an ethnic majority controlling a territory unilaterally seceding from a wider State is de facto possible - after all, that's how Bosnia & Herzegovina itself was created as a State in 1992-1995 -, but.. at the condition than a bigger party helps it, as NATO did in Bosnia on the behalf of the Bosnian Muslims during the Bosnian War. And if major NATO countries support the secession of Kosovo & Metohija from Serbia by the Kosovo Albanians, the same countries oppose a similar endeavor for the Serbs from Bosnia & Herzegovina seceding Republika Srpska from.. Bosnia & Herzegovina.
The "de facto" hence primes on the "de jure" in several steps of the independence process of a polity, and on the de facto matters, Republika Srpska currently lacks of momentum to obtain what it desired for since its inception in 1991-1992 : being recognized as master of its own destiny, in order to rejoin an union with Serbia that it never wished to leave in the first instance when Yugoslavia still existed.