Unless there is going to be some increase in the rewards pool, I don't see how this could be the case. I'm sure that some authors might stand to earn more, but it's not clear to me exactly who would benefit and who would have to absorb the cost of the change.
Excellent point. I likewise have no idea who will earn less vs. more. I'd guess quickly that curators may earn more since the existing 30 day payout pays nothing to curators. Beyond that it is unclear.
My understanding is that votes are reset at the end of the 24 hour period currently... any votes after that currently start from scratch and hence why the 30 day payouts are minuscule.
Under the 7 day dispensation all votes within the 7 days are added to the top, with none starting from the bottom... therefore there would a substantial difference in the value the later votes add if this is the case.
As to who benefits...
How long posts will trend... will be determined by the UI and could still be limited to a short period.
Posts which receive later votes will cannibalize the rewards of posts that no longer receive votes in the 7 days.... authors of inactive posts are likely to see rewards fluctuate more as they did before 4th July and still do slightly now during a day.