If this system gets big enough whales will probably hire teams of the best curators (in reality this probably includes a combination of humans an bots working together). So indeed whales will in fact be the best curators.

If you are a whale and don't curate well you will have a sub-par ROI and lose value. So you will likely either improve your curation, sell your stake and invest in something that doesn't require you to do something you aren't good at, or, eventually, lose it all.

On the other side, some will curate well and by virtue of getting an above-par ROI, become whales. Someone will be the Warren Buffet of Steem curation.