I decided to go down the rout of having SSD drives in my system.

I backed up all my audio and I am now putting windows back on.

I was planing on putting X1D Producer Expanded back on my rig but when I placed my order for X2 today it got me thinking........

Would I be better waiting for the release and having a fresh install ?

Can anyone think of any pros or cons for a fresh install of X2 rather than sticking it on top of X1 ?

I think it makes zero difference.  X2 is going to be able to install side/by side with X1, and you are worrying about keeping a hard disk, "neat and tidy."  

The hard disk does not care what is installed on it.  It only cares what is defragged.  The ram only cares what software is engaged during, "real time use of the computer."  The registry gets cluttered, and takes gentle pruning and maintenance...   Something you will have to do no matter what you install...

IMO you should install X1 again. We don't know what kind of problems X2 will have upon release and there will likely be a learning curve anyway. If you have both installed then you can keep working with X1 as you wrap your head around X2 and aren't left without a DAW if X2 has any show stopping bugs. Also you can load X1 projects into X2 to see how things have changed. That's what I'm gonna do.