So one is left to wonder what problem will be fixed. It seems to me like there are several potential issues: 1. Standard ABS issue where friction braking is reduced due to wheel slippage. 2. Regeneration cut-off issue where regeneration is stopped due to wheel slippage. 3. Engine decides to start up while regeneration is happening. Note there's no wheel slippage going on here. Logic forces the motor/generator to switch from generator mode to motor mode since that's needed to restart the gasoline engine. Which of these is/are being fixed? 1. I'd guess they won't be fixing the first one since it has been reported many times across the previous generation of Prius, and there's been no recall for those cars. Right or wrong, this is assumed to be normal ABS operation, and indeed it has been reported for cars made by various manufacturers other than Toyota. 2. Maybe, but perhaps not since again this situation has been reported with the previous Prius generation and nothing was done. 3. I'd bet that this is the one they're fixing (if it's really happening). Having the motor/generator switch from generator-mode to starter-mode while you're lightly braking could indeed cause real acceleration and not just a momentary pause in braking that most people on the forum seem to think is happening.
The "switching" is not as profound a mode-swap as you think, it's just an adjustment of various torques as needed. Please don't cloud the issues any more than they are. . _H*
