For now we get the sizes that they can fit in scraps that are left from TV manufacturing. Samsung's version is a bit better than Alienware's because it doesn't have old Nvidia Gsync module. Alienware can do max 144Hz at 10-bit. It drops to 8-bit at 175Hz. Samsung can do full 175Hz at 10-bit.
The good thing is. OLED monitors are coming. It won't be long before we see 27" 1440p and 32" 4k panels.
A lot of people are buying $2.000 QD-OLED TVs. How many gamers buy $700 gaming monitors? Until they produce enough TVs they won't be cutting whole panels in gaming monitors. When they can sell monitors for $400-ish we will get more QD-OLED goodness. For now we get the scraps from TV manufacturing.