There is no fixed date but as per the track record once in a couple of months. 45 to 90 days you can say. & if anyone has an official MVS (formerly MSDN) subscription then those ISO can be downloaded directly from there MSDN/MVS website, apart from that, you'll find plenty of mirror links here at MDL & over the internet.
I'd like to understand if knowing ID (6594 or 6595) may be useful in order to download ISO for ourselves.
Why the sad face? If you are worried about the performance impact of the security features you should still apply the microcodes (and/or UEFI firmware updates) and disable those in the registry. Microcodes were regurarly released over the last two decades or so to fix many other issues, not just security but potentially crash/corruption-inducing bugs or compatibility (with other HW parts like some RAM chips and such). Even Microsoft used to include the most critical ones for a decade or so, thus this is nothing new really.
@SM03 You should already know the answer. Anyway, when they will be available, you'll find SVF files into the dedicated thread.
The ISOs that you have created yourself: are they identical to the ones released by Microsoft? I mean their SHA1 hashsums are identical?