I think if we go into the season with our current corners, it'll be highly matchup-specific, but in general Butler and Gilmore will cover the outside receivers with Rowe backing them up, while one of the Joneses will primarily handle slot guys. But that would probably be highly matchup-specific, and there are lots of teams whose WR corps would lend well to having Butler in the slot.
Basically, I guess we could look at this as insurance to make sure that we're not just one injury away from Cyrus Jones or Justin Coleman playing on the outside.