For a very select set of problems (factoring and discrete log), quantum computers are exponentially faster than classical computers. For a few (including np-complete problems), they are quadratically faster. For everything else, they're no faster. (When I say "faster", I really mean the runtime of the best known quantum algorithms is better.)

For the forseeable future, quantum computers will be much smaller than classical computers -- the article is about Google building a 49 bit QC and how that would be a breakthrough. So for the forseeable future, they'll be separate components, used for special cases.