From Software isn't known for cross-company platforms. They aren't Kojima Productions.
That said, the Large Sword of Moonlight in Demon's Souls seemed like a subtle reference to the MOONLIGHT laser blade from Armored Core, FS's main series. --- "When Garland knocks you down you're going to ****ing stay down." - __Skye__
Moonlight Sword is pretty much a given, though I wouldn't necessarily expect it to still be in Large Sword form. Maybe this time it'll be a straight sword with built in spells. That would be getting closer to the original from King's Field.
I'm not sure an easter egg for Demon's Souls would matter much, since the whole game is already like a giant reference to it. >_>
I'd actually like to see more swords from King's Field show up. Like Triple Fang or Seath's Sword. --- I am snazzier, hot, hot rant. Warily slight as. Croak rush, OK? Weirder, almighty make out. ::)
Something that would make an nice Easter Egg is all the sets of armor from Demon's Souls mounted on stands scattered throughout the world --- 010101000110100001100101001000000100011101100001011011010110010100101110
Don't get me wrong, the reference would be awesome, but keeping the reference obscure enough to avoid having to give royalties and keeping it recognizable... I'd be impressed. --- "Ware wa Sanger Sombold. Aku o Tatsu Tsurugi Nagi!" The last thing Evil hears before it is Cleaved in two.
... Now that's a good reference. Thought I think the go through mountains is a bit extreme. --- "Ware wa Sanger Sombold. Aku o Tatsu Tsurugi Nagi!" The last thing Evil hears before it is Cleaved in two.