The Khajiit are a feline race, but that doesn't mean they all have the skeletal structure of real cats. If you want to talk anatomy, digitigrade feet would be horrible for a bipedal creature. A more sensible (biologically) anatomy would be like in Oblivion but with hand-paws and hand-feet instead of spray painted human hands and feet like in Oblivion.
For the Argonians I'm not sure, but I liked the concept art. I'm personally hoping the Khajiit don't have freaky legs. I know some like it, and I know it's fantasy so skeletal structure isn't important, but they are so goofy looking and structurally unsound in Morrowind I hope they don't go that route.
I also hope they get the tails right, though most professional artists don't mess that one up. The tail extends from the end of the spine.
Yes, thank goodness I'm not the only one who thinks like that. Cats (and a lot of other animals) in our world are digitigrade because it allows for more efficient movement
as a quadruped, had cats evolved as bipedal they would not be digitigrade, their feet would be flatter to the ground with their heels (hocks) making contact with the ground for better strength and balance in a bipedal stance, and their knees wouldn't be right up against their body, they'd be around about where our knees are.
When it comes to Argonians, a lot of quadrupedal reptiles are not digitigrade anyway (their entire foot for the back legs is flat on the floor most of the time), and the bone structure and points where muscles attached onto the bones in bipedal dinosaurs also show that they walked with their foot fairly flat to the ground.
ie. no bipedal beast race ought to have it's hocks (the equivalent of our heels) halfway up its legs, if they had developed as bipedal they would walk with their feet flat and heels down.