I'm gonna be a wishful thinker here and predict the Lock Capsule has to do with Black and White. There's plenty of evidence to support development for BW may have began at least a year ago, overlapping with the end of production on HGSS (
3D testing in HGSS, BW being announced in April using the DS as its platform when Game Freak had likely
obtained 3DS/other next-gen development kits at least two months earlier, etc.), so I wouldn't call the prospect too far-fetched, especially since there could be a high level of connectivity between the Pokémon generations. Although, maybe it's possible the item might just be some sort of mechanism to prevent game crashes (like Arceus's ???-type).
Concerning the Azure Flute though, I really doubt the Pokémon Company is even going to bother with it, at this point
. Since HeartGold and SoulSilver don't contain the Hall of Origin event, the mindset of the Pokémon Company is probably not focused at all on Sinnoh, especially now that it's the better half of a year later since Platinum was in the limelight. I don't know if events are still going to be supported for Gen.IV in the future, but with Black and White's Japanese release imminent, there's an increasing potential for Nintendo and its Pokémon-related subsidiaries to completely break away from the past... Though if it were to be distributed, I'd imagine it'd be a Platinum-only Wi-Fi event, in the same vein as the Member's Pass and Oak's Letter.