It's now confirmed that Marvel Studios will be holding a Hall H panel at San Diego Comic-Con 2019. Back in 2014, Marvel took the unprecedented step of announcing their entire Phase 3 slate in a private event. More recently, though, the company has become a lot more secretive. In fact, right now Marvel is refusing to comment about any of their post-Phase 3 slate.
Marvel president Kevin Feige is known for playing the long game, to the extent that he's confirmed he has the next 5 years or so planned out in detail. But he wants viewers to enjoy every step of the journey, and as a result is attempting to focus attention on just one or two films at a time. In fact, Feige has even suggested he thinks the Phase 3 announcement back in 2014 may have been something of a mistake that backfired. That's why he's kept current plans back until after the theatrical release of Spider-Man: Far From Home. With this year's San Diego Comic-Con taking place just weeks after that release, most fans had assumed there'd be a Hall H panel with some major announcements this year.
The official SDCC schedule confirms that there will indeed be a Hall H panel by Marvel Studios. It will take place on Saturday July 20, running from 5:15pm to 6:45pm PT (1:15am to 2:45am GMT, 8:15pm to 9:45pm ET). The panel description is short and to-the-point; "Marvel Studios president and producer Kevin Feige and surprise panelists provide an inside look at the ever-expanding Marvel Cinematic Universe."
Marvel only tend to put on an SDCC Hall H panel when they have something they believe will wow the audience; they carefully build these panels into their marketing schedules, and in fact have no qualms about skipping a year if they aren't ready to make any announcements. Marvel even skipped SDCC 2018, much to the surprise of fans who thought the studio would celebrate the MCU's 10-year anniversary in style. So it's safe to say this year's Marvel Studios panel will be one of Comic-Con's highlights.
Of course, the interesting question is just how much detail Marvel will go into. For all they're avoiding any official announcements, Black Widow is currently filming in Budapest and a number of projects are known to be in various stages of pre-production, including the likes of The Eternals, Doctor Strange 2, and Black Panther 2. It wouldn't be a surprise to get confirmation of some of these, while there may also be more Spider-Man news. It's generally believed Marvel's deal with Sony requires them to produce a Spider-Man movie in 2021, which may well mean Spider-Man 3 comes out as soon as 2021.
It's difficult to say whether or not Marvel will release details of their slate beyond the next couple of years, though. As noted, Feige has previously hinted he views the Phase 3 announcement as something of a mistake, so he may be unwilling to repeat it. At the same time, though, Marvel's current reticence had built up expectations to an intimidating degree. The pressure to do something radical at SDCC 2019 will be intense.