Wirecast has always allowed us to record multiple versions of the same stream on the same hard drive as 2 separate files in 2 different resolutions as well as different formats.
This is an extremely useful feature which we have used often and is still not available in vMix without recording to an external output on a separate device.

We often need to record 2 versions of the stream on the same laptop hard-drive without connecting another external device - e.g. one lower res H264 file for websites and another high res file (usually in a different format like AVI or MOV) for post-production editing.

When will vMix finally incorporate this very useful feature?

There is no such button layout in my version of vMix (vMix HD).
No 1 and 2 buttons are shown - just a drop down for the 'default folder' with a browse button.
What about making this feature available in all versions like Wirecast does?

The deal is that it has for years, always been available (in all my regular versions of Wirecast from 5 onwards) which I had bought at that time for just $450. If Wirecast could have provided that feature standardly, why can't vMix do the same? Btw I am a big vMix fan and have since switched from Wirecast.