Vorons max at 350mm^3. Adding more in x or y probably isn't a great idea, but you could probably push z some more. Rat Rigs use larger extrusions and scale to 500x500.

I have a 350mm Voron. I havent completely filled my bed yet, but I have printed some fairly large parts on it. But man, big volume = long print times. I've gotten some... very large numbers out of my slicer. Volumetric flow isn't that high, so I'll likely grab a larger nozzle and print even wider (currently at 180% layer width on a 0.4 nozzle). Still, a 500mm part would take... a very long time