Microsoft has made it known there will be no .ISO file for Windows 8.1 available to the general public.
"Consumers" here really means any copies of Windows 8 that weren't purchased through Microsoft's Volume Licensing programs. So a small business with 20 PCs to upgrade, for example, will have to do them one at a time via the Windows Store – so that's 20 separate 3.5GB downloads.
The Windows Store is the only way for consumers (non-enterprise, non-IT Pro) to download and install Windows 8.1. No ISOs will be made available, so each device needs to be updated individually via the Windows Store.
Since I started this discussion, Microsoft has introduced a Media Creation Tool that makes it easy to download a .ISO file and create bootable media:
The new downloader allows for selection of:
⦁ Windows 8.1 Version