Demon's Soul has never been multiplatform. The IP is owned by Sony.

Many people who worked on Demon's Souls and Dark Souls 1 didn't work on Dark Souls 2. This is what they should've been working on.

It's exclusive most likely because Sony contracted them, just like they did for Demon's Souls. Though Sony dropped the ball with Demon's Souls and they're likely making amends with this one. Besides that From will receive funding/experience for a next-gen game too, and support from Sony so it would be dumb to say no.

A Dark Souls 3 or whatever probably wouldn't be exclusive though.

Many people who worked on Demon's Souls and Dark Souls 1 didn't work on Dark Souls 2. This is what they should've been working on.

It's exclusive most likely because Sony contracted them, just like they did for Demon's Souls. Though Sony dropped the ball with Demon's Souls and they're likely making amends with this one. Besides that From will receive funding/experience for a next-gen game too, and support from Sony so it would be dumb to say no.

A Dark Souls 3 or whatever probably wouldn't be exclusive though.

Dropped the ball? I though Demon Souls was a critical and sales success?

Ah I see. Unless they have multiple teams, due to  DS2 just recently being released, I can't imagine seeing this game until 2016 (2 years after DS2).

You are a bit confused allow me to explain, Demon Souls is the FIRST souls game and it was CO-DEVELOPED by sonys first party studio SCEJ and From Software, therefore SONY owns the right to the Demons Souls IP, however the game was originally only released on Japan, becasue Sony didnt thought that the game would sell well on the west, so after some good sales on Japan Atlus published the game on the west (because Sony wasnt gonna do it...) and then the game came to be a succes in both sales and critics (even wining some Game of the Year Awards). despite Sonys original desbelief of its succes on the west. so later on due to Demons Souls succes From Software saw the potential of the souls series but since they didnt own the IP (as i said Sony owns it) they created a different game that was a "SPIRITUAL SUCCESOR" to Demon Souls and they released it in multiple platforms and BANG the soul series took form.

Later on SONY realized their mistake of not growing the Demons Souls IP, (admited by Yoshida himself) and they decided to make another game (wether a sequel to Demons Souls or a new Souls game), so they went to From Software and decided to AGAIN CO-DEVELOP the new souls game with Sonys First party studio SCEJ and From, thats why darks souls 2 was able to be produced and delivered while at the same time PROJECT BEAST was being developed as well with the help of SONY, so chances are that SONY will own this new IP or it actually is DEMONS SOULS 2... (an IP that SONY already owns) in fact there is a video (i will link it at the end) that shows a graph that contains all of the developers of the souls series and you can see that critical developers (including Miyazaki the creative director) of Demons Souls and Dark Souls are absent from Dark Souls 2, so they are more than likely working on PROJECT BEAST.