Model number SM-G730A will sport a 4-inch display, SM-G3815 a 4.5-inch display, SM-G9105 a 5-inch display, and SM-G7102 a 5.2-inch display. No further details are yet available on the SM-G9105 and SM-G7102 phones. But User Agent Profile strings found on Samsung's Web site pegged the resolution for the SM-G730A at 480x800 and the resolution for the SM-G3815 at 960x540.
Based on their low resolution, the 4-inch and 4.5-inch phones will almost certainly be lower-end devices. The other two phones could be more on the high end. But for now it's all just speculation until Samsung spills the beans on these upcoming additions to its lineup.