According to the Korea Herald, Samsung decided to "play it safe" with its next year's flagship phone and it will adopt the same basic design as in its current Galaxy S8. The 2018 Galaxy S9 will use a 5.8" Infinity curved Super AMOLED display (and the S9+ will use a 6.2" display as used in the S8+).
It is likely that even if this report is true, Samsung Display will use an enhanced display. Even though the display used in the GS8 was "the best mobile display ever" according to DisplayMate - there is still room for improvement, for example higher resolution (good for VR), better efficiency or a larger color gamut.
This is somewhat of a surprise, though. With Apple readying its first OLED iPhone which some believe will be a very attractive phone, Samsung may need to attempt a more radical new design if it wants to attract the high end of the market.