Walter Blaser wrote:
... need to uninstall in case you want to run both versions (2014 and 2015) alongside for a transition period.
You need to return your license in your customer account in order to be able to get the license code for the 2015 version. This means that you will not be able to reactivate Studio 2014 in the future, but it will continue to run on the PC where it is currently installed as long as you don't deactivate it. This is what SDL is explaining in the instructions you mention.
In essence: you can keep using 20145, but only on this PC, You won't be able to transfer it to another PC.
Studio 2015 can be installed without any problem alongside 2014, as they are installed into different folders.
To simplify Walters words: Install 2015 and be happy with it. The rest still will be there, unless you buy a new computer or reinstall your old one. (sorry Walter)
[Edited at 2016-03-31 21:03 GMT]