Does Ex design have a master page?
And export spec like in scetch-will this functionality exist in the programme?
Currently XD does not have master pages. I know it's not exactly the same, but currently you can use symbols to update content across multiple pages.
The Adobe User Voice website https://adobexd.uservoice.com is where Adobe accepts new features requests. It looks like something similar has already been requested, so you can up vote it to add your voice.
XD does not currently had a spec export like Sketch, but I think it was at Adobe MAX that they showed some work on a feature for easing the handoff to developers. Hopefully that will be coming to a future version.