Soviet Union has a problem of large minorities who will use attempts at reforms to break away. Not all but most western ones will. Are they allowed to leave or are their leaders sent to place of heavenly peace? The former will weaken SU, the alter will show Gorby is not serious about reforms.
The Baltic States yes if they get the chance and are allowed to organize a mass-movement, everyone else it depends for example the idea that the other republics abandoned Mommy Russia is BS despite the propaganda they (Ukraine for one) spout nowadays. Yeltsin pulled Russia out of the USSR first (utterly stupid move) after that everone else had little choice.
If the reforms are successful and the Soviet population sees economic improvement and a rise in living standards, and maybe a fall in political corruption things would remain stable. Remember it was only
after Gorby buggered up the Soviet economy and at
same time gave all the nutters & malcontents a chance to openly oppose the central government that things started to go badly wrong.
It was avoidable with more prudent leadership.