Strangely enough, the league may not benefit from it at all.
As huge of stars as some of these players are outside of the USA, they are not even slightly popular inside the USA (MLS). They are not on Pepsi, Coke, or any other commercials (ok Henry was on ONE Gillette commercial). They are rarely in the news for more than 2 seconds (hell I've never even seen Lionel Messi on ESPN Sportscenter ffs). / exaggeration.
The only player with any clout to come in to MLS is Beckham because of his appearance/world wide appeal and not because of his footballing skills.
Henry and Raul will not be a big deal outside of the fans already inside the MLS circle because they are just not marketable.