Apple has begun sending email notices asking its registered Mac developers to submit their OS X Mavericks-optimized apps. The timing of the communique is especially eyebrow-raising given the October 22 media event invites went out today as "we still have a lot to cover".
Jumping ahead of oneself, one might conclude this signals an imminent Mavericks release. In reality, it'd clearly make more sense to release Mavericks alongside the refreshed Mac notebooks.
For what it's worth, a source that stepped forward this morning has pinpointed an October 24 or 25 release date for the upcoming Haswell-based MacBook Pros...