It's now mid-May, we should be getting news by now but not even an indication that anything is coming up. Hopefully these games aren't barebones like (imo) SwSh we're.
They don't announce when we're getting news until shortly before it happens (usually the day before at this point). I wouldn't worry too much that we have no idea when the next news is coming (in terms of the exact date, we usually have a pretty good idea of what months they reveal major news), we never do. Just the nature of their marketing now.
Not really indicative of anything.
Major info for SWSH dropped on June 05, 2019 through a Pokemon Direct. But HOME news did get dropped on May 29, 2019, just like we recently had. Of course, I would LOVE to have news before this month ends. And nothing says that they need to release news in June, especially now that there's no E3 and there's no Treehouse to showcase gameplay.
Anyway, this is what was revealed in the direct:
- Zacian, Zamazenta, Gossifleur, Eldegoss, Wooloo, Corviknight, Drednaw
- Leon, Hop, Prof. Magnolia, Sonia, Milo
- Dynamax, Max Raid Battles, Wild Area, Rotom Phone
- Boxarts revealed, release date announced
Then on the Treehouse Demo (June 11, 2019):
- Yamper*, Impidimp* (shown on the game but not officially revealed)
- Nessa
- Y-Comm, Poke Ball Plus compatibility
- Dexit
If we're going by this, the next trailer hopefully reveals the region name, boxart, release date, box legends, several new Pokemon, Rival, Professor, at least 1 Gym leader (if any), and a few gameplay mechanics.
This is pretty standard stuff to get in the first big info dump after release, or at least by the end of June. It's practically a given that we'll get that kind of stuff soonish. Look at what we got for some of the previous generations as well:
XY
May 2013 Corocoro (Leaked May 11, 2013):
- Region revealed to be Kalos and Lumiose City revealed. Full region map also shown
- Kalos Dex divided into Central, Coastal, and Mountain Kalos
- Fletching, Helioptile, Pancham, and Gogoat revealed
- Gogoat riding revealed
E3 2013 (Aired June 11, 2013):
- Fairy type revealed. Sylveon, Gardevoir, Jigglypuff, and Marill confirmed to be retyped to Fairy.
- Spewpa, Vivillon, Noivern, Skrelp, and Clauncher revealed.
- PSS, Pokemon Amie, Horde Battles, and Sky Battles revealed
- Release date confirmed to be October 12, 2013
June 2013 Corocoro (Leaked June 12, 2013):
- Viola and Alexa revealed. Viola confirmed to be the gym leader of Santalune City.
- Shauna, Trevor, and Tierno revealed, and the opposite gender of Calem/Serena is also confirmed to be rival. Vaniville Town revealed to be the starting town.
- Scatterbug, Litleo, Flabebe revealed
SM
First Trailer Drop (Aired May 10, 2016):
- Region revealed to be Alola. Map of Melemele Island shown.
- Rowlet, Litten, and Popplio revealed to be starters.
- Kukui and Hala revealed, but their roles are not specified.
- Release date confirmed to be November 23, 2016 for EU and November 16, 2016 for all other regions.
Second Trailer Drop (Aired June 2, 2016):
- Solgaleo and Lunala revealed as mascot legends
- Kukui revealed to be the Professor. Hau and Lillie also revealed.
- Rotom Dex revealed
June 2016 Corocoro (Leaked June 11, 2016):
- Zygarde 10% and Perfect Zygarde revealed
- Rockruff and Komala revealed
E3 2016 (Aired June 14, 2016):
- Pikipek, Yungoos, and Grubbin revealed
- Battle Royale revealed
Third Trailer Drop (Aired June 30, 2016):
- Tapu Koko, Charjabug, Vikavolt, Drampa, Togedemaru, Cutiefly, and Bruxish revealed
Most of your list isn't exactly a bold prediction. The region name, full region map, Professor, Rival, mascot legends, a few prominent Pokemon (probably the regional bird and/or rodent and some other random ones), gameplay mechanics that are especially emphasized in the game, and release date are practically a given for the next trailer, and if not then, then most likely by the end of June. If there are new dex features (which I'm not sure there will be, but I could certainly be wrong here), we'll probably hear about them too. Gyms might be a bit later, but if they're tied into a major gameplay change we could see them. New burst mechanics are about 50/50 (I'm inclined to believe they'll save this for June/July, they probably have a lot of other things to cover).
In particular with SV, I think they'll also elaborate on some of the mechanics that tie into the open world and go into more detail on how the open world changes the gameplay. If we can explore areas in any order or complete gyms in any order, I think they'll confirm that in this trailer (and I think that would be the most likely way we hear about anything gym related this early). They'll probably also clear up how catching and battling will compare to LA and older games, if not by directly stating any new mechanics, they should at least show how with gameplay footage.
EDIT: Added extra reveals until the end of June to give a better idea of when these crucial pieces of information were revealed.