Yes Pentax has the 645D; which is quite impresive; especially for the price.
Pentax 645D Digital SLR Camera (Body Only) 17971 B&H Photo Video
But when a 40mp digital back on a medium format may not be enough; one can always use either en existing 80mp back or a newer version of one to be released soon. Here's the link to the new version due out soon...
Leaf Credo 80 MP digital camera back
Or perhaps you may want to wait a bit... I'm not even sure who will be releasing this new hardware; as I haven't yet seen the hardware or the new back in person. But i've seen the images. Expect a 110meg back out within less than eleven months or so.