So far it is only for downloads bought from The FlightSim Store (their main outlet). Over the next couple of weeks FSS will update all the wrappers and you can log into your account to re-download and you will get a choice of P3D or FSX. There is no limit to how many times you can download a purchased file from your FSS account.
I've been putting all my FTX scenery into FSX and using the Migrator tool to link it to P3D. But when Prepar3d v2.0 is released, I'll re-download all my scenery with P3D installers and put it straight in. There are one or two minor annoyances with the UI by having it in FSX. Once I've done that I won't have any need for FSX; I only use it now to store these older FTX scenery files.
Ian
