Hard to say for sure, I doubt that they will last as long as Film camera...But the moving parts will be sure to have a certain amount of wear and tear. And I am sure we all take far more shots with digital.. But at the rate of 50,000 images in 4 years you will be safe for another 4 or even 8 years.  Canon rate the shutter for 100,000 to 150,000  And quality of build seems to be improving with each new model..

For sure the mechanical parts will be most prone to wear such as AF motors.  Also contacts may also wear out even on flash cards.  Batteries will also only have a certain half life..  I would also think that the elements will degrade the internal electical parts of the camera in time as the seals wear.. Or if you constantly expose them to the heat and cold or high humidity.. 
 
But chances are you will have replaced it with a newer model anywhere near the time it will wear out, and most parts can be replaced it will depend much on what the camera is worth by then.. MY 10D is still going strong and cost me £1200 when new but doubt it will be worth more than £250 now, so if it required repair I would be spending maybe more than it was worth to fix it.. If and when it ever breaks down

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt