Can someone please tell me why windows is still releasing these previews.
I thought now that windows 10 is released that would the end of these previews
You have not kept up to date.
Long before Windows 10 RTM was released on July 29th, MS has already told us that we have 2 options...............
1. To continue participating in Insider Program. MS will continue to develop new builds and Insiders will get them when they are released.
2. Upgrade to Windows 10 RTM on July 29th and be done with the Insider Program.
However, if you change your mind, you can still switch back to Insider Preview program from Windows 10 RTM.
And does someone know if m/s upgrades the Release ISO's that it makes available for public d/l.
For example would there be any difference in the current iso as compared to the one they listed on the first day of release of 10.
I am not entirely sure what you are asking. ( English is not my first language.)
If you are referring to the Windows 10 RTM ISO,
there is only one release.
It can be downloaded using the Media Creation Download Tool.
http://www.microsoft.com/en-us/software-download/windows10
If you meant something else, please elaborate.