To the contrary. And in addition to that, MF format film 'blows away' anything your K20D can produce. And I'm a dSLR fan too, although I only have an *ist DS.
No need to quibble. K20D @ 1600iso B&W produces a long tonal scale, very little noise (does look like modest TriX grain @800). This is more than 3X higher detail resolution than *istDS, though that's a fine tool as well. My impression is that K20D soundly beats 645 but doesn't rival 6X6 (I like square images). This is all irrelevant because nobody's making MF cameras anymore, and if someone was after maximum detail they'd be shooting LF anyway, or making elaborate 27frame mosaics digitally.
I shot a lot of 6X7 and 6X9 and it's certainly capable of fine images of static subjects ...this kind of discussion can go on forever...8X10 film is infinitely beyond 4X5.
In more practical terms, none of the MF cameras have ever approached the ruggedness of K20D (or other medium-top tier DSLRs), and that's a real issue for active photographers... fragility is one of the reasons Mamiya rangefinders were terminated.
To the extent that we care about image quality, the current Mamiya MF DSLR and top Nikons/Canons do far exceed 645 film in every respect, not to mention my Pentax, and they're obviously afforadible to profitable pros.
I've processed film properly (ie Nikor/Kinderman stainless) in a bathroom or wherever, in the daylight, using a changing bag for thirty-plus years, using darkrooms for printing up until I got a Nikon V scanner. Perhaps happily, the total demise of good scanners (unless Plustek's smarter than they seem) will make a few heroic die-hards return to optical printing necessary for their serious goals( by definition they only print their own and don't tolerate $2 scans).