The more I think about it, it's online for me.
Having everything unlocked from the start is good in one sense but for me it gives me no reason to play offline.
Being forced to run a certain car on a certain track to progress through the career isn't something I'm too interested in, I'm not a trophy hunter either so.
I had plenty of fun clean races on GT5/6 and met loads of cool people so I'm expecting more of the same on PCars especially with the crowd this game is aimed for.
That's why almost all of my free time now is spent driving cars on GTR2 with my DS4 with the NAP mod and no aids. Closest thing I'll have to PCars until I get PCarsI will be splitting my time between both Career mode and online mode. In the first few days after release, I will probably focus on Career mode until I get a proper handle on the cars/physics. Having experienced an early version, I can tell you that this will not be a "just get in and drive" racing game. It will take effort and practice.
Very soon after that though members of my league will be back in action in online mode.