Oda is going to use Loki to upscale Shanks:
Given that Oda already set the standard that Shanks defeated Loki, I think that he'll use Loki as a measurement to show just how powerful Shanks truly is, as well how far Luffy is compared to him by showcasing Loki having the upper hand over Gear 5 Luffy, showing that Shanks is stronger than someone who Luffy has to potentially grow to beat.
Given that Oda already set the standard that Shanks defeated Loki, I think that he'll use Loki as a measurement to show just how powerful Shanks truly is, as well how far Luffy is compared to him by showcasing Loki having the upper hand over Gear 5 Luffy, showing that Shanks is stronger than someone who Luffy has to potentially grow to beat.