I was surprised to discover that FLIR offer ROICs of up to 2k x 2k pixel resolution (the ISC1404). It's quoted as being suitable for InSb and SLS sensors, meaning it would be usable at MWIR or LWIR. Information is somewhat sparse, and none of us are likely to have the facilities at home to build a sensor to attach to it.
Moving over to actual cameras you can buy (with enough cash, and the appropriate export paperwork) I was impressed by the uncooled T1030sc at 1024 x 768 LWIR, <20mK. If you want higher resolution there's the 1280 x 1024 X8500 series for MWIR or LWIR (7.5-10.5µm), <40mK. I know I'm starting to sound like a FLIR advertising brochure but I think these are seriously impressive. And probably seriously expensive.
The fact that this information is on public display makes me wonder what other toys are lurking in the shadows...
Has anyone else come across any publicly-available information on very high resolution cameras or cores from other manufacturers? The only one that springs to my mind is Ulis' Pico1024, at 1024x768.