Very worrying. The environmental impacts of Bitcoin are absolutely horrendous.
If bitcoin powers the post-modern financial industry, the resource savings will be enormous.
They will all still be there, there will just also be lots of machines calculating SHA256 hashes
[EDIT: Corrected the numbers to match what you wrote. It is irrelevant, though -- if you get a gigahash for X watts with PCs, you'll use X watts to get X gigahashes with a 1W/gigahash ASIC.]
To put it another way, not going to 30kW of ASICs is equivalent to taking 30kW of PC mining hardware and turning some of it off (in a pre-ASIC world where PCs are the most efficient mining hardware available).
I don't think we'll get to a point where BTC has a significant footprint anytime soon.