It's nearly impossible but if that happens it will pretty much look like when eritiria did it ... Ofcourse if the transition is not peaceful there will be people getting chased out of oromia and also oromos getting chased back to oromia ... On top of that the new country (oromia) borders every single state except tigray so the current ethiopian country will be divided in two or multiple places ... Then there will be the complication of addis ababa b/c about 60% of Ethiopia's wealth is consentreted around A.A and around it so that will create some complications... Then some of the officials that are currently in position have to get changed cuz they are not citizens of whatever is left of it....then the parlama will get messed up ... There will be border conflics ... Economy will crush due to a significant drop in export materals like coffee and gold ... And again if the transition is not peaceful oromia will not allow trade b/n different parts of the remmaining ethiopia by air or ground then trade and management will be difficult ... And more endless problems are inevitable so do not expect all of this to happen ... Not just oromia but also the other major states