Everyone seems to be on similar page here... all eyes on Switch this year.

Sony will be mostly already announced, with a surprise or two thrown in.

Microsoft will be all about Scorpio and every game that takes advantage of it.So include games like Forza, Crackdown 3, and one surprise, and you are good.

Nintendo will be the most interesting, since they are the ones fighting an uphill battle.Yes, they will show more of Mario Oddysey and XC 2, but other than that, we dont know nothing.I think its safe to say that we will see what Retro is doing, and we will probably glimpse at the Zelda DLC and maybe a bit of Fire Emblem 2018, but I guess there will be alot of surprises.

Wish list (you ain't getting any realism from me!):

Sony:
Don't really care that much since I don't have a PS4. Sad times indeed :/

Microsoft:
The new elder scrolls would be amazing, quite a few years since last time now and I can't wait to get back into tamriel once again!

Nintendo:
Where to start?
Metroid by Retro, alternatively an western RPG in the veins of the witcher
Xenoblade 2 for winter 2017
Splatoon 2 update coming with four player split screen (if they don't have that at launch, wich I doubt)
Fire Emblem Switch footage, 2018 release confirmed.
Animal Crossing Switch
Pokemon Stars Switch 

Pikmin 4

Battalion wars 3

Endless Ocean 3

...

that's quite a lot when I look back at it. Think I would be quite happy if only one of them happened to be honest. At least I can dream ;D

Edit: I see the editing screwed up the space between the text, the punishment for being greedy I suppose :/

I'll do my wish list because I stink at predictions

Nintendo:

• Super Smash Bros. 4 w/ all DLC and all the content from the WiiU and 3DS versions together at last
• Retro Studios game 
• Metroid 5 (I guess this could be the Retro game)
• One of the above: new Excite, new F-Zero, new Wave Race
• Bayonetta 3

I wish everyone would do a recorded event. Those live things are so awkward, bloated, overproduced, and overlong.

I NEED to know what Sucker Punch is doing.
Also, a new God of War trailer or demo would be epic.
Media Molecule HAS to show something about Dreams, its been forever.
Star wars stuff from EA
Insomniac's new game

Sony: I think, hope/want that they will show:
-TLoU2
-GoD Of War
-Days Gone

Nintendo: This is tricky, Nintendo could have lots games to show: Retros game, Next Level Games game, Metroid Prime, Pikmin 4, Animal Crossing, Pokemon...some Wii U ports, all games like Mario Odyssey, Xenoblade 2, Splatoon 2, Fire Emblem...that are already unannounced, some 3rd party esclusives. But of course big question is what Nintendo will decide to show at E3, but Nintendo could easily blown away this E3 depending of what they will decide to show.
I personaly that will see again Mario Odyssey, Xenoblade 2, Splatoon 2, Smash Bros 4 port, Metroid Prime, Pikmin 4 and some 3rd party exlusives like Beyond Good and Evil 2 and Mario Rabbids.

MS: I am not really in what MI doing or what I would expect or love to see.

will be interesting when first Insider rumors will be around,;)

I understand what you're saying but the recorded events would have to be less awkward, bloated, and overproduced themselves.  I mean, when you have Reggie and another grown man sitting down to play with Skylander Amiibo or you have Miyamoto wandering around looking at temples, then you're hitting the hat-trick for awkward, bloated, and overproduced.

Still the absolute best show I've ever seen at an E3 was Sony's from last year (or was it the year before?) where they showed games one after another.  Live or recorded, both can be done well or done poorly.

Those examples are a bit unfair though, they're not awkward because they're recorded, they're awkward because they were basically made to fill up time during Nintendo's 2015 presentation seeing as they had nothing else to show. That whole presentation was filler now that I think about it. Worst Nintendo E3 ever imo =P