For October, you have almost 100% chance of scoring walk in permits. A lot of people back out then.
Yes, and it's not just October. In fact, I didn't even bother to enter the lottery this year because it was so easy to get a walk-in last year and the year before.
Overnight permits are not as easy, but if you have a day or two of mid-week flexibility then you are likely to snag one or more.
@TechDoc, Mt Langley is another fun 14k hike, especially through Cottonwood Lakes, but don't give up on a Mt Whitney summit this year.
edit: For those who were able to get a permit in the online lottery, be sure to confirm when able to -- before the deadline.