At this moment, I'm afraid re-mixes are necessary. I know of 3 films in post that are waiting for the studios to OK a home Atmos, near-field mix.

While the rendering processor might do an adequate job of re-routing the individual assets and combining them into fewer channels, I don't believe they are sophisticated enough to determine if the sources being combined are correlated or uncorrelated. When you combine 2 assets into 1 speaker do you pad by -3dB (uncorrelated) or -6dB (correlated)? That's why the mixers re-balance the audio.

Meridian Advocate