wsnz:
Technically we're not guaranteed to get the KS investment back, but I think it's unlikely the all would be lost.
I think his statement about funding people over 65, relates to NZ Super being funded from general taxation, at the same time as KiwiSaver is also being deducted. It's likely (IMHO) that NZ Super will be supplanted by KiwiSaver or at least means tested against KS balances, at some point in the future. Under that scenario today's taxpayers are paying twice, for only one benefit.
There are few guarantees in life, but KS funds are invested by independent financial entities so it's unlikely - short of a major crash - that the money would be lost. It's not (as you know) a scheme like UK NI where it's effectively an extra tax that just gets swallowed up in the general govt finances.
I'm less sure about KS replacing super, or super being means tested. I'd like to think that such a proposal would be so unpopular as to remove any chance of a govt proposing it from gaining power, but the politics of envy can be a strong force. If you start testing means against KS balances you're on a slippery slope - do you count real estate value of the family home, family trusts, etc etc?