Titanfall has only just been released, and we're already talking about the sequel. However, we have good reason to. Titanfall was never originally planned to be a Microsoft exclusive, however it seems that Respawn decided to partner with Microsoft after being sent the offer to, most likely for extra revenue reasons.
It's probable that the choice was on EA's hands, but even though Titanfall has been confirmed as an Xbox and PC exclusive, the rights to Titanfall have not been sold to Microsoft, which means it's completely possible that the Titanfall sequel could be cross-platform.
Vince Zampella stated on Twitter that Respawn have not sold the rights to Titanfall to Microsoft, and although there hasn't been any confirmation, many Respawn developers have hinted that a Titanfall sequel for all consoles could be very possible.
Titanfall 2 will most likely be made, and EA seem to be very confident that the title could do extremely well as a franchise, but EA would be stupid to leave out the potential of the PS4, too. For this reason, I think it's very likely that Titanfall 2 will be made available for the PlayStation 4, as well as the Xbox One and PC. Of course, it's hard to guarantee that at this point, but it would make perfect sense if it did happen.
When that will happen is a different story, though. EA seem to be keen on focusing on Medal of Honor and Battlefield, still, so it may be a three year development cycle for future Titanfall games.