The plan is you'll get to find out what one of the announcements is this evening (Pacific Time) at IGN. The rest of the announcements will come in the following day(s) since there are embargoes on the information from the event.
And as all Peep Show aficionados know, there's no reason not to trust Alan Johnson.
If Internets rumors are anything to go by -- and Wikipedia has told me they are -- today's announcement could likely be The Walking Dead game(s) based on the hit AMC TV show which again was based on the graphic novels.
In other words, Monkey Island 6 and Maniac Mansion 3: Day of the Tentacle 2 might still be a few days away. Telltale's embargos make Apple seem downright friendly.
Update: Two titles are confirmed by All Things Digital: Walking Dead and Fables, based on the DC comics.