Currently there is only 1 high speed "D" train plying the Beijing-Shanghai rails, taking just under 10 hours (9 hours, 44 minutes), basically trimming the time of the overnight "Z" trains by 2 hours. The "D" train leaves in the late morning and gets in late in the evening, but rumor has it that before the end of the year, there will be an overnight "D" train making the trip.
With the current price for the "Z" and "T" overnight soft sleeper trains at RMB499, it will be interesting to see if the price for a "D" sleeper berth will remain at RMB499 or go higher. If the price remains the same, it will definitely be an attractive option, most likely leaving around 9-10 pm and arriving at 6-7 am. While plane tickets can sometimes be had cheaper than the soft sleeper train tickets, this option is far more convenient, dropping you off in each of the city centers.
Of course, the "bullet" train that will make the trip in 5-6 hours is still a few years down the line.