It would have most likely been a descendant of Liu Shan, the Guangwu Emperor was not the closest to the throne in direct descent, but his success in restoring the dynasty meant he clearly had the mandate of heaven. The Wei court was categorized by meritocracy at first, but as power shifted away from the imperial family it relied more closely upon conservative aristocratic landholders, and the take over by the Sima family has been described as a return to an older style of rulership. The Jin greatly empowered its relatives to prevent a collapse of royal authority after a few distant relatives were done away with, but this only opened up the door for the war of the 8 princes. Yet the Wei emperor's decision to marry a relatively powerless aristocratic women of humbler birth was also an intentional move to avoid the fate of the Later Han's powerful Dowager clans that controlled court affairs in times of regency.
One might assume that Liu Shan, or one of his descendants, becoming emperor would solidify the idea that the Emperor must be of the Liu clan. This would make second time power reverted back to the old imperial house, and if a fourth time happens later down the line the Emperor may become an inviolable position with the idea that family leadership and the mandate of heaven could be passed around from different branches of the royal line, but not outside of it. This could potentially evolve into a Japan like situation, but that is neither here nor there at the moment. How long authority remains with the Lius, and how long the Han Dynasty lasts in its third iteration is more difficult to answer. There were demographic and climate-related reasons that contributed to the Jin Dynasty's collapse, but the ultimate root could be found with the War of the 8 Princes, which led to the Wu Hu Rebellions. Provided the takeover of China is less devastating to it than the 8 Princes, which may have brought the taxable population down to under 15 million, with China's population itself not being too much greater than that, then it may be able to properly deal with the Wu Hu and the emerging northern Xianbei threat.
But a major drawback is that the imperial examination system may never rise up. The examination system's most early infancy was with the Cao Wei and Jin states. While there was an Imperial academy and personal tutelage among scholars and schools of scholars, the idea of a national bureaucratic testing institution was first brought forward with Chen Qun's system. How big his part was in this process can be debated, but that it first gained prominence in Wei cannot. If Shu Han does not continue it, then the future of China's bureaucracy and its relationship to the scholar-gentry's rigid education process could be made far more fluid and dynamic, or conversely result in a regression in standards and Confucian ethics.