In the piping world, 2D will never vanish despite the utility and increasing use of 3D. Aside from strictly 2D drawings such as P&IDs and isometrics, there are a number of advantages to having the plan and elevation drawings in 2D only, such as the ability to send out multiple small projects to different companies despite the affected drawings all referencing the same model. It sounds a little backwards, but plants rarely stay in their original as-built condition so there is a constant update of drawings (OK, maybe not in all cases - I've worked on some where the isometrics don't match the plan drawing, and field photos show something completely different...).
I think the biggest stumbling block we have right now is the number of different 3D piping design programs, *none* of which will talk to each other if at all. I don't think there is near as much variation in say structural or civil design but I could be wrong. Some clients have older large scale software like PDS but for an EPCM to start up with that just to use existign models requires a huge investment up front so the projects have to be pretty large to be cost effective. So we end up receiving 2D drawings, modeling some of the existing facilities in whatever we're doing, and send back "flattened" 2D drawings in a fraction of the time and cost.
