Just announced in Raider.IO Discord channel:
"We've been listening to all of your feedback regarding whether or not to reset scores with the upcoming M+ Battle Rez changes. We can see the benefits and drawbacks from going either way here, but in the end we've decided to not reset with 7.3.5.
We recognize that building up your Raider.IO score is a time investment, and we don’t want to reset it unless absolutely necessary. Any time we’ve started a new season in the past we’ve had to think through the ramifications and decide if there was enough reason to justify the inconveniences caused by a reset. In this case, we felt the negative impact of a reset would outweigh the positive.
This isn't a decision we made lightly, and we know not everyone will agree, but as always we try to do what we think is best for the community as a whole."