Unconfirmed (but likely)
These are the studios that are most likely going to E3 and what game they're showing.
DrinkBox Studios - Severed
Clapfoot Games - Fortified
Metanet Software - N++
Ubisoft Toronto - ??? (Ubisoft has their own press conference at E3, but what specifically is coming out of Toronto is still unknown).
If you're a Toronto GameDev and at E3, then be sure to let me know!