Boeing's answer to the A-380 was the Sonic cruiser. A smaller airplane that was faster. 9/11 killed the sonic cruise and the 787 was born. A smaller airplane with the range of the larger airplanes.
The -8i is set to hold on to the 400 seat market. The freighter already has a ton of orders (and did kill the A-380 freighter)
I recall the proposed MD-12 - never got beyong the proposal stage. The line drawings that I saw looked a lot like the A380.