Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.

As it has not been released, we can only speculate.
Yes, you probably have to pay for it, as it will be a brand new release.
It may, in all probability, be able to be installed as a separate install, next to v3, as it is not an update of v3.
Why do you expect it to be free? You do not get Office 2016 for free, if you already have Office 2013, as an example.
Having said all that, the above is all speculation.
The best people, probably, to answer any P3D queries, would be within the Prepar3d forums on the Prepar3d site.
The way P3D has worked in the past is that you pay for the new version i.e. pay for V1 then again for V2 again for V3 etc...but you don't pay for the version upgrades i.e V3.1 or V3.2 or V3.3 etc...So we'll be paying I'm sure .
I think the recommendation would be for a total fresh reinstall because from 32 bit to 64 bit - but I dont know what I'm talking about here !