Rajdhani's upgrade to 160kmph will be mostly in NCR territory. So far SCR has not done any 160kmph upgrades anywhere on it's routes. Shatabdi's 160kmph, if possible at all, will be only the SC-Wadi section. Wadi-Pune is barely fit for 110kmph, not to mention, not even fully-doubled yet. Even SC-Wadi itself is a tricky route for 160kmph, as a lot of changes will have to be made in P.way to sustain such speeds. So, for now, its safe to assume that the speed upgrade is only on paper and will take many years to materialize (Raj might get high speed clearance in NCR though).
For the 26 coachers, when the proposal first came out a few years ago, they said that...
more... there were PF issues at HYB, and that was why Gautami was chosen over Godavari, AP and Charminar at that time. I don't know if those constraints have changed now.