Microsoft has made it known there will be no .ISO file for Windows 8.1 available to the general public.

Windows 8 Iso Download Msdn Version

That is, Windows 8.1 with Update ISO image file isn’t available to download from Microsoft right now. Which means that, if you have plans to perform a clean install of Windows 8.1 Update by downloading Windows 8.1 with Update ISO image file from Microsoft, you’ll have to wait for a few more days to get your ISO file. However, Windows 8.1.

'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.

Can I get an ISO download for Windows 8 pro?

Windows 8 Pro Iso Download

No. There will be no ISO for retail and OEM Windows 8. The only upgrade path is through the Windows Store if you do not have access to TechNet or MSDN. (source: http://blogs.windows.com/windows/b/bloggingwindows/archive/2013/10/17/windows-8-1-now-available.aspx Brandon LeBlanc in the comments 'We're not releasing the ISO images to folks who don't have MSDN and TechNet subscriptions. Best way for everyone else is to update through the Windows Store. '