What is typically done on the bike when it goes back to the dealer at 20,000? 
You can go to hd-com, -> OWNERS, -> SERVICE CHECK-UP for updated information. For a Touring bike it would read something like:
AT 20,000 MILES / 32,000 KILOMETERS
ITEM SERVICED
PROCEDURE
NOTES
Engine oil and filter
Replace
Oil lines and brake system
Inspect for leaks
1
Air cleaner filter element
Inspect, service as required
Tires
Check pressure, inspect tread
Wheel spokes
Check tightness
1
Primary chaincase lubricant
Replace
Transmission lubricant
Replace
Rear belt and sprockets
Inspect, adjust belt
1
Throttle, brake and clutch controls
Check, adjust and lubricate
1
Jiffy stand
Inspect and lubricate
1
Fuel lines and fittings
Inspect for leaks
1
Brake fluid
Check levels and condition
3
Brake pads and discs
Inspect for wear
Spark plugs
Replace
Electrical equipment and switches
Check operation
Engine idle speed
Check adjustment
1
Steering head bearings
Lubricate
2
Air suspension
Check pressure, operation and leakage
1
Wind deflector bushings
Inspect
1
Cruise control
Inspect disengage switch and components
1
Saddlebags
Lubricate hinges and latches
Critical fasteners
Check tightness
1
Engine mounts and stabilizers
Inspect
1
Road test
Verify component and system functions
NOTES
1. Should be performed by an authorized Harley-Davidson dealer, unless you have the proper tools, service data and are mechanically qualified
2. Disassemble, lubricate and inspect every 50,000 miles (80,000 kilometers)
3. Change D.O.T. 4 and flush brake system every two years