Hard to call it in the future, but still, in a deflationary currency any %, even 0.0000001% is a good thing. I've heard calls for negative interest rates (which obviously can't work in practice, but you get the idea).
Can't really see rates THAT low being attractive. Risk sets a lower-bound on the acceptable rate. So for even a rate of 1% per year to be acceptable you have to be confident there's a less than 1%/year chance of default/failure for it to be better to invest than keep coins in cold storage. At that rate you're already into the area where lack of a deadman's switch would be sufficient to make investment in something unattractive (average life-expectancy being under 100 years).
