Samsung has done very well with the Galaxy S6 and the Galaxy S6 Edge smartphones. Demand for the S6 Edge with its curved screen has been very high and Samsung has warned that supply won’t be able to meet demand. The hold up in production for the S6 Edge so far has been availability for the curved screen.
Rumors are circulating that Samsung will have a new larger version of the S6 Edge available this summer. The exact launch date isn't known, but rumors suggest that it will launch in August. The current S6 Edge has a screen that is 5.1-inches in size. The rumor suggests that the new device will have a screen in the 5.5 to 5.7-inch size.
Considering that the Galaxy Note 4 has a 5.7-inch screen, perhaps what this rumor is hinting at is a new version of that device with curved edges. It's hard to say at this point since there is no official confirmation.
The Japanese translation of the rumor is sketchy at best. It would be no surprise for Samsung to launch more curved screen devices, the S6 Edge has proven to be very popular, and with the right apps and notifications, the curved edges can be as useful as they are pretty.