A few notes:
After several days of October being "sold out" except for very sporadic cancellations, they added/moved some inventory yesterday. Today, as of 10am, both parks are still open for reservations, and this weekend is open, too. This is only the 2nd time in October that same-day reservations have existed for Magic Keys after the parks open.
December currently has no DL-start days available. Every Monday-Thursday is open for DCA start, nothing is open for any Friday-Sunday.
So far, no date has "sold out" the day it's released to Magic Keys. Saturdays (and holidays) go by far the earliest. For January, the first two Saturdays are sold out, and Saturday the 15th is DL-start only, but all other days are open for both parks.
Next-day reservations have consistently been pretty available in the evenings. I try to check in 3-4 times a night, just out of curiosity, and usually at least one park is open when I check. Of course, I've been basing this off of this availability calendar (
https://disneyland.disney.go.com/av...egments=ticket,ph,ap,resort&defaultSegment=ap), and as mentioned on other threads, it appears that cancellations may be Magic Key-level specific, so YMMV depending on what level of Key you have. But I'd say that at this point, if you have the ability to make next-day reservations in the evening and are willing to refresh a lot, you can feel pretty confident about getting in.
Assuming all of my reservations slots are full, once I enter the turnstile, I can make my next reservation, right?
Yes, that is how it has worked for us.