It would have been a major boost both in morale for Sertorius’ army and in his ever strong personal prestige, he could have incorporated the remnants of Pompeius’ army into his own, and would have very likely beaten Metellus at Saguntum, if the latter had still decided to give battle. After that? Sertorius had two options, either gather his augmented forces, exploit the momentum, and attempt to march into Italy, or keep pressing Rome to grant him the amnesty he so desperately sought in OTL. The Republic would have never allowed him to retain an independent potentate, no matter what it would have kept on sending armies against Sertorius until until he eventually succumbed.