Elon Musk's September 14 roadmap update drives current trader sentiment, detailing Grok 4.8 as a 2.5-trillion-parameter model on xAI's new C++ stack that would finish training that week before entering reinforcement learning. The announcement positioned 4.8 as a noticeable step up from Grok 4.7, which shipped September 21 with stronger long-horizon coding and agentic performance at competitive $2/$6 per million token pricing. xAI's rapid cadence—multiple 4.x releases since mid-2025—has traders watching for swift RL progress and any early benchmarks that could accelerate a 4.8 launch, likely in October, amid competition with models from OpenAI and Anthropic.