I think now that we can visit across world in the same logical data center (we can even go crossing data center now), attending other world Eternal Bonding Ceremony should be technically plausible to implement.

This is comparable to entering Zadnor instance on other world:
-max player of 72 at Zadnor vs 82 at EB
-much much smaller instance size and object amount on EB instance.
-multiple running zadnor instance with irregular spawn time vs scheduled 2 hours max EB instance

I hope someday we can see this being implemented. Maybe even sending invitation through mogmail to our cross-world friend