It seems to me that the economics of the industry are against this project as opposed to the A380. The success of the 747 is largely down to the fact that the operating costs for each flight don't rise as quickly with the size of the aircraft as the revenue from each flight (defined by the number of pax) does - in economist speak, the marginal cost of transporting a passenger rises less quickly with increasing load than the marginal revenue. The condition for economic efficiency in perfect competition is production where marginal cost=marginal revenue. That is to say, it is efficient to build bigger aircraft until the higher operating costs catch up with the higher revenues per-flight.
We aren't dealing with pure economics but with economics and engineering, so this point will be defined by a limiting factor which is sufficiently costly to overcome that it outweighs the gains from a further move up in size. At the moment, the first limiting factors for aircraft size are the terminal facilities required to handle very large aircraft. (The A380 design brief included a condition that the aircraft must be able to use terminals designed for 744- sized aircraft.) The next would probably be connected with handling very large loads of pax on the ground before engineering restrictions were reached.
The reasons for all this are in the cost-structure of airline operations. The cost of transporting a planeload of pax includes overhead costs that have to be met to begin with and are either fixed or semi-variable (like the cost of capital), costs which vary per-flight (i.e. staff, landing charges, air traffic charges, tax, and fuel as far as it is determined by mileage), and costs per-pax, like passenger handling, meals, and a proportion of fuel. The biggest chunk of the costs is made up of the fixed and per-flight costs. Therefore, larger loads per aircraft (bigger planes) win out over more flights with smaller aircraft, all things being equal. Whereever this holds, (i.e. main-line routes) larger aircraft win out.
In the future, we can expect that the price to airlines(in a market solution) or the availability (in an administrative solution) of flights (i.e. slots, landing fees, terminal capacity, air traffic charges, green taxes) is going to be squeezed. This is a consequence of rapid growth in air traffic combined with environmental problems. The current generation of airports and air-traffic arrangements are filling up, and expanding capacity is becoming politically very difficult. It is to be expected that the environmental costs of aviation will be an issue. Therefore, there will be some form of demand-management of the number of flights. This may be achieved through a free market in airport slots or by setting an administrative cap on their number. Given that passenger numbers rise faster than economic growth, the pressure will go somewhere.
Boeing's solution with the SC appears to involve smaller numbers of passengers - i.e. larger numbers of aircraft (wouldn't you!) - serving larger numbers of airports. This last idea seems very unlikely as widespread airport development will be even more unpopular than concentrating at the hubs (where only the people who currently whinge will whinge!). Generally, Boeing SCs will use the short-supply resources - the per-flight costs - much more than A380s and lift fewer pax on each flight. It don't take John Maynard Keynes to work out that this means less revenue and higher costs - so either no profit or very high ticket prices. Which means very few SCs!