http://www.dwavesys.com/en/dw_homepage.htmlPrice tag of only $10,000,000 and that's probably old tech now since it's commercially available. Bitcoin is already vulnerable and has been since it was created.
Consumer products will probably be out in 2020.
Not.
Eventually if it does become a problem, you do something against it, same thing happens with pirating, the gov will never stop pirating, nor will quantum computers or anything of the sorts stop bitcoin
AFAIK the most advanced quantum computer today can only add 2 digits where the sum is 7 or lesser....
It wont be like one fine day you would see physicists come out and announce "Today we have built a quantum computer advanced enough to do double sha256 and mine bitcoins @ 1 gazilion PH/s" .... Im pretty sure before then, quantum computing would become common in day to day life for simpler tasks... and the algo would have evolved taking that into account.
The risk, if there ever is one, is not from the mining aspect but rather from quantum computer being used to crack private keys, but im certain devs will adapt to stronger key algo by then.