I really hope this is gonna be true.
Imagine, Ariana will end up releasing Side to Side and Greedy as final singles AFTER October so they both will be eligible for 2018 Grammys (Best Pop Solo for Greedy and Best Pop Duo for STS).
Subsequently, Ariana will DEFINITELY release a collab for that Duo submission. I thought Side to Side would be great for that but to be honest, a feature with OneRepublic would have more chance than other features in DW. 1R is famous for making good and solid music for ADULTS, who Ariana has been in trouble to make them listen to her music. Ariana needs to spread her audience who usually buy CDs to listen in their cars, and OneRepublic is also a good album seller too (I think?). They can make a difference this time since Jet Lag (Simple Plan ft. Natasha Bedingfield).
So, Dangerous Woman era be like:
1. Dangerous Woman (Mar-Jun 2016)
2. Into You (Jun-September 2016)
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3. 1R ft. Ari (July-November 2016)
4. Another Christmas material.

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5. Side to Side (Jan-April 2017)
6. Greedy (2017's summer song bookmark me)
Truth Teller said he was aware of third DW single would get shadowed by this, but I mean, Into You is just half way of its full run, so I would say this 1R single will slay side to side with Into You, not the third one.