SDCC is from July 19-22, so it starts on Thursday. October comic solicits will drop the week of July 23. So I expect publishers will have some fairly major announcements and reveals over the next week.
A fairly significant recent development was DCs announcement that G Willow Wilson (co-creator of Ms. Marvel, Kamala Khan) will be taking over Wonder Woman with art by Cary Nord beginning in October. She has also teased at another major announcement for her coming today at noon PDT.
Marvel will be announcing more details on its next X-Men book, X-Men Black. This continues the recent "color themed" X-Men titles. No details have been released about the book or its creative team yet, save for this cover art featuring Magneto.
To get in to the spirit of SDCC,
Comixology has a fairly large list of significant sales going on. I am definitely picking up some Image releases I have been waiting on.