Currently I have a 3-monitor setup, one 30" (2560x1600) display and two 24" (1920x1200) displays. If the pixel density were to remain about the same as the 30", this would equate to about a 42" 4K monitor. The current 4K monitors seem to be in the 24"-32" range. Higher pixel densities give us buttery smooth text and crisp images at the expense of workable screen real estate. My personal choice would be a monitor somewhere around 35". Screen real estate is important to me. If Apple releases a 4K display that is the same size as the current model, I would be somewhat disappointed. What size would you like your 4K monitor to be?