Once these four Treasure Swords were handed over to Po Kong, they would no longer continue to grow stronger. Although Xin Yun could also enhance them, he wouldn't do so, since he never did things that weren't beneficial to him.
However, even though the Treasure Swords themselves could no longer be strengthened, as Po Kong's strength increased and the purity of his energy improved, under his control, the might of these four Treasure Swords would also progressively increase.
The power of the attacks using the Zhu Xian Four Swords depended on two factors, one was the power of the swords themselves, and the other was the strength of the user. The same Treasure Sword, wielded by people of differing strengths, would unleash utterly different levels of power.
