And for the week of Sunday April 18, BOG and CRT were posted around 1am Eastern time this morning. So to recap, for the week of Sunday, April 18, this happened:
Friday, April 2--Hours were extended (only one week though which was unfortunate since my stay straddles the weekend)
Sunday, April 4--Activities at HS may have become available per NEMouse's report.
Tuesday, April 6--Epcot restaurants opened up early am between 3am and 7am Eastern and AK restaurants were added between 4 and 5pm Eastern
Wednesday, April 7-BOG, CRT and other MK restaurants added at around 1am Eastern
Unsure about HS. I'm guessing they might have dropped around 7am on Tuesday since I was able to get a 9am Oga's reservation at that time. HS only extends one hour each way (from 10-7 to 9-8) so they probably don't add much, if any. Even before the extension, when the hours are at 10-7, they take reservations up to closing (and perhaps even after based on some reports.)
This was a great question BTW as I was wondering myself. Unfortunately, I'm not sure there is a clear pattern that is followed from week to week.