Once we've reached such a future, all basic necessities will be so cheap and plentiful that no one minds having the government pay for them. So I see no reason an "extreme income tax" will be necessary.
I would argue that we've already reached that point. If the government was streamlined by market processes and we ceased blowing surpluses on wars we could easily fund a safety net.
Here in the UK we spend about 30 billion squids a year on defence. About a third of that is service pensions, another third goes on the bureaucracy/long term projects and another third on the actual services themselves.
That's half what we spend on healthcare and one-fifth of what we spend on welfare. Anyone who thinks that by cutting defence spending a government can suddenly afford anything is dangerously misguided.
Here in the US, we spend at least $600 billion a year to start, plus another $30B+ on pensions, plus shitloads of black budget on intelligence. This amounts to about the entire UK budget, just on yearly budgeted defence.
None of this includes the cost of actually fighting our ridiculous wars: the cost of the Iraq shenanigans alone will be well over a Trillion dollars even if Obama pulls out this year and no more money is spent after that.
