The logical argument against that seems to be that indexing costs aren't Google's major problem and cheaper indexing wouldn't provide much of a competitive advantage.
Even better relevancy may not be enough as most people believe current search technology is "good enough". It would have to be very innovative. If nothing else, they're a good acquisition target for an existing search company looking to further reduce costs and increase profits or allocate more resources towards more computationally expensive algorithms (spam filtering, semantics, content targeting, etc.)
I think if they can index significantly faster, then it's highly likely they'll be bought up by Google or the competition for their indexing tech before anything in mentioned in that first paragraph happens.