PS4 party chat supports 8 people
Sony made today a post on the official PlayStation Blog with a quite comprehensive Q&A for the upcoming game Killzone Shadow Fall.
When asked in the comment section how many players will the PlayStation 4 support when party chatting an employee answered that up to 8 players will be able to discuss at the same time, just like PlayStation Vita.
Combined with cross-games chat feature, the new and improved voice chat, PlayStation 4 will encourage players to socialize more.
Source: PlayStation Blog