First off, there will be 3 777's with the crew rest facilities. One alread has the "Condo" installed. The other two need to be modified. You need 3 to operate the service. Two flying, and one in Mx as needed.
The MD-11's that they use now have a tough time operating the NRT service. They are load limited with all the fuel that they have to carry. Even at that, they often have to stop in PDX and get gas before coasting out. The 777's will less load limited and will not have the problem with needing to stop for gas.
So, Delta will convert the NRT service to the 777 as planned. They've wanted to for a long while.
Now, as for the MD-11 coming back in numbers, who knows?? I don't think they'd want to, it is a small fleet type, and expensive to operate. At last check, I thought they still had one or two 767-400's in the desert. I'd look for those to some back well before the MD-11's.