Even though earlier rumors suggested Samsung will adopt an LCD for the upcoming GS5 phone, it was later reported that the GS5 will actually adopt a 5.2" WQHD (2560 x 1440, 560 PPI) AMOLED panel. Today, at a display technology roadmap seminar, Samsung confirmed that indeed they are developing a QHD AMOLED panel.
Samsung will not stop at 560 PPI. The company is actually planning an even higher density panel - a UHD panel that will feature 860 PPI. It will be very hard to justify such a high density on a mobile device, but I guess it's a marketing race that is hard to stop. At any case, it seems that Samsung will be adopting the Diamond Pixel architecture for those high resolution displays.
During the seminar, SDC stated again that it plans to use flexible AMOLEDs in new markets - specifically the wearable and automotive markets as these are not suitable for glass-based rigid displays.