I think an important thing to note is that in situations like this, they CAN be better for it next time around, but this is not guaranteed.
There's certainly a component of self learning in it as the next time the boys are defending a close lead they'll know what did, and didn't, work last time but I also think there has to be an institutional element to it lest we create or enable a losing culture.
I work within the startup field and all high growth tech young companies (or however you want to define a startup) that go through accelerator or incubator programs, or receive VC investment, are given mentors to protect the developing companies against the mistakes of those who walked before them.
Could something like this work for the u20s?
Could this years leadership team be parachuted into next years camp?
If even only for one night, it could be structured something like this:
5pm: arrival and each member of the leadership team mingles with their respective position / unit (eg backline/forward pack).
5.30pm: the leadership team presents on their own journey through the last u20 RWC, what they learnt, the standards required and the highs / lows of their experience. They could also hand out email addresses or phone numbers for the players to direct any future questions to.
6pm: dinner with the team.
7pm: video analysis of moments that defined their RWC. For instance this years lads could watch the second half and advise where they went wrong and how future teams could learn from that.
It'd be relatively cheap and informal yet would serve to create a "fraternity" around the team and hopefully inspire the u20s lads about how close they are to professional footy / higher levels (eg if Tuipolotu and Perese returned next year they have that Super experience under their belt to speak from).
I fucking hate typing on my iPhone but hopefully you know what I mean.