Can I just tag this? Cause I don't like to make predictions, but I do love to see other people fail/succeed at their predictions.

Why not ? Hahah 

Hmmmmm.... I'll go with Polyphoney digital and therefore the new game should be Granturismo 7 ( or whatever they'll call it ) which is slated to be released this holiday season.

I also want to add another one:

13. Gameplay footage of GOW 3: remastered will be shown together with a release date.

1. Uncharted 4 trailer / gameplay / information
2. Uncharted: Nathen Drake Collection gameplay / information
3. Batman Arkham Knight trailer
4. Metal Gear Solid V trailer
5. Assassin's Creed Syndicate trailer
6. Persona 5 trailer / gameplay / information
7. Tearaway Unfolded trailer / gameplay
8. Call of Duty Black Ops 3 trailer
9. PS4 & Vita price-cut (and 1TB PS4)
10. Street Fighter V trailer
11. Horizon announcement
12. Ni No Kuni 2 announcement
13. 15 new Indies on Playstation platforms
14. 3-8 new Vita game announcements
15. New Killzone game announcement
16. Information about Project Morpheus
17. Sony Bend PS4 horror game announcement
18. Shenmue 3 announcement
19. The Last Guardian returns or a new game from the Shadow of the Colossus developer

1. Uncharted 4 stage demo
2. Uncharted 4 trailer
3. Ratchet and Clank game trailer
4. At leasts one of the 4 F2P games will get a public alpha/beta which can be downloaded before the end of the week.
5. The Last Guardian will be re-announced with a trailer and it's launching this year.
6. Media Molecule will announce their Play, Create, Share 'game'
7. Media Molecules new 'game' is made for VR but not exclusive to VR.
8. Guerilla Games will announce their new game (no gameplay at the show)
9. Sony London will announce a new game
10. Zindagi Games will announce a new game for Project Morpheus.

11. A new PS+ TV-show/series will be announced.
12. David Perry will announce a change or addition to the PS Now service.
13. Project Morpheus will be priced.
14. Project Morpheus will be rebranded PlayStation VR.

15. Asssassin's Creed: Syndicate gameplay trailer or demo, exclusive content will be announced.
16. Persona 5 gameplay trailer or demo.
17. Star Wars Battlefront gameplay, exclusive content will be announced.
18. Launch plans for No Man's Sky.
19. Trailer for Call of Duty and exclusive content will be announced.
20. Street Fighter 5 gameplay trailer or demo.

21. ThatGameCompany will announce a new game for PS4.

3.  New Rockstar game will be announced at the show.

Note: Sony don't do one month exclusives so the content will be exclusive for 6 month minimum.

If you don't mind i'll just write stuff that isn't entirely confirmed or almost certain(so no "Uncharted 4 gameplay" or things like that cause everyone knows it's happening..same for R&C and a couple of other games..morpheus talk, Activision butt kissing for Destiny)

500gb model cut to 350, new 1TB model costs 400.
New Parasite Eve from Square Enix, PS4 exclusive. Coming this holiday.
Level 5's PS4 JRPG is a new IP. Coming 2016.
Gravity Rush 2 officially coming to Vita+PS4, bundled with GR1 (at least on PS4).
GG's Horizon is unveiled, coming Summer 2016 (or May-August)
Bloodborne expansion revealed

I think that's it as far as new-ish things go.
I've thought for a long time MM would announce its new game, a holiday 2015 title, at E3 but with Tearaway unfolded not even having a release date yet i'm starting to get doubtful. Which reminds me, I guess they'll finally tell us its date.

Sony already showed the Ratchet and Clank trailer today so I've changed my prediction.

GG will announce it's new game

SSM will announce God of War IV

TLG will be shown

Gravity Rush 2 will come to PS4 instead of Vita

Destiny's next expansion will be shown

AC Syndicate will be shown

Uncharted 4 will get more gameplay and maybe a release date

Street Fighter V will be shown and maybe a release date

NMS will get a release date

Battlefront gameplay

Hmm all I can think of for now.

Nice list. :) the dlc is for what ? The 6 month exclusive dlc i mean.

1. Uncharted 4 gameplay, with beta announcement and a trailer with a release date Feb. 2016.
2. After Uncharted 4, Sony would remind gamers that there is a Drake's Collection coming in Oct. with Uncharted 4 Beta.
3. Sony announce their partnership with Activision is stronger by announcing Destiny's new expansion and showing Call of Duty Black Ops 3 for the first time at a Sony conference.
4. Capcom trailer for Street Fighter V.
5. Sega announce Phantasy Star Online 2 console exclusive to the PS4.
6. Shenmue 3 and Shenmue Collection coming to the PS4, exclusive.
7. Mafia III announcement with exclusive DLC.
8. A PS4 bundle with Metal Gear Solid V, (special edition)
9. A montage of indie support like Rime, Everybody Gone to the Rapture, WiLD, Tomorrow Children, I Am Bread, etc.
10. A new indie game announce from thatgamingcompany exclusive to the PS4 and PC.
11. No Man's Sky gameplay and a solid release date for Fall 2015.
12. The Last Guardian re announcement for Fall 2015.
13. 10-15 minutes presentation of Project Morpheus.
14. Sony's going to drop the name Morpheus and give it a new name with release date and price point.
15. Shuhue Yoshida shows up and announce Level 5 new game, Dark Cloud.
16. Tearaway release date.
17. Media Molecule will announce their next game, works with Project Morpheus, but only as an option.
18. 1Tb PS4 for $400.
19. Brag about the success of Bloodborne and announce their expansion.
20. Battlefront gameplay and exclusive content. 21. A game teaser from Rockstar.