Yeah FEDNAD, all I can say is check the links I posted which have the (un) official entry lists for most of those tourneys, save for the DC which is a bit more vague.
Djoker's website only has AO, then Dubai, then IW/Miami.
And Nadal's taking all of Feb off. Fed is on the entry list for Rotterdam FWIW.
And yes, Nishikori will be top 20 after AO, so he's in the 1-20 range. Everyone, use this site when choosing players as it has updated rankings for guys who may have moved up/down post AO.