I think there should be an option in the settings menu to allow the player to set themselves as a preferred host for gameworlds. My internet is around 800 up and 600 down so I never have any trouble hosting games. Perhaps you have to pass a connection test to enable the option to stop everybody from enabling it.
But what matters isn’t exactly your upload or download speeds, but your proximity to other users.
Zak explains this and how hosting will work in the future in this really awesome post.