To be honest, I don't know .. Maybe Bloodborne 2?

Well, if it's a surprise I would't be expecting it! But what I'm hoping for is TimeSplitters 4 and hopefully some Final Fantasy VII and Resident Evil 2 remake footage.

Retrostudioooooooooooooooo
and Pikmin 4 maybe.

Not exactly all of them as new announcements or surprises, but I expect Nintendo E3 to go like this:

Fire Emblem first footage (2018 Oct or delayed to Feb 2019)
Pokemon Switch (Nov 2018)
Smash 5 (Sept 2018 with the online) - the big focus of the show
Metroid Prime 4 first footage (2019)
Retro Studios game announcement (2019)

Not especific order, but I believe these are going to be the highlights.

From Nintendo i expect Retro's new game and Pikmin 4. I also think there is a big chance that Nintendo will announce Metroid Prime Trilogy HD. As for other publisher i think we are going to get Splinter Cell, Resident Evil 2, DMC5 and of course Sony will announce something. Wouldn't be surprised if Guerilla was developing a new Killzone alongside Horizon

Pikmin 4
Animal Crossing
Retro's new game

C'mon Pokemon + Animal Crossing.

Retros game
Pikmin 4
Smash 5
Probably Metroid Prime 4
Pokémon will be shown either at E3 or at an event before or right after E3.
Fire Emblem will probably get its own direct before E3 cause they don’t wanna overshadow it with all their other games, plus it got its own direct last year too. So we’ll see.
And hopefully Animal Crossing.

edit: also probably Bayonetta 3. Idk though. That would be one hell of an E3. Pokémon and Fire Emblem will probably be reserved for a different time. 

From Nintendo I think Retro Studios new game and Pikmin 4 will be what is announced. I also think Animal Crossing or Pokemon will be announced, which ever one is happening, as a holiday 2018 title. I was thinking about Fire Emblem, but i'm going to guess the official reveal of that game happens a few weeks or a month+ before E3. It will probably be revealed around the time of E3, but slightly before it, so they can just show off gameplay at E3. We'll also probably get a ton of Yoshi gameplay, too ... wow ... that's going to be a great E3 for Nintendo if all of that happens. I expect them to fuck it up, somehow.

For Sony, I think they've proven that they are going to rely way more on previously announced projects than completely new ones. They garner hype by showing off games that they've revealed and teased many times. They did have a lot of new announcements during E3 2015 and 16, but that was mostly because it aligned well with how long it took for their exclusive projects to get underway (a lot of the devs worked on PS3 till the very last year and they had to get some of their more niche studios to get used to working on bigger projects). So basically ... what you see now, is probably what you will get. You will see The Last of Us 2 gameplay, Final Fantasy 7 Remake gameplay and episode 1 release date, MediEvil gameplay and release date, Days Gone gameplay, a small bit of Ghost of Tsushima(possibly just cinematic, possibly SOME gameplay), and Spiderman gameplay and release date. You are probably going to see one surprise, it might even be a big one, but this is definitely an E3 that's going to be based around just showing off games instead of making crazy announcements. Again, there could be one, maybe even two big announcements(though I'm guessing one), but I doubt it will be as crazy as 2015 or 2016. Oh yeah, and you'll probably get a Shenmue 3 tease. And maybe something from From Software.

Xbox is by far the hardest to figure out, and it's not just because they have little games, but because it's hard to know if they're bluffing when they say they're preparing for a big E3. Could easily be a big PR tactic but then again with a new console out maybe it's true now more than ever. I'm going to predict they're announcing a new Halo, a new open world IP, a new Forza Horizon 4, and possibly a Banjo Kazooie game. Yes, the last one isn't likely, but oh well. I'm also going to say, that Halo 6 has about a 50/50 chance of releasing later this year, or next year. It's really critical that 343 takes their time with this game in particular ...

Also, I predict that the new From Software game will either be a new Souls game not connected to the previous ones, OR a new IP ... 

Another rerivial of one of Rare's lagacy games.. hoping to see Perfect Dark, Battletoads, Conker or Banjo Kazooie. Thats all i need.