They'll pull the same shit they did for GTA5, guaranteed.
There isnt any guarantee really. The first one was talked about coming to PC years and years and it just never came. Giving it a PC port would have been a pretty logical move. But they never made it. Who can say why. Think RdR is going to be a console series, like God of War or Uncharted. I generally have a feeling like Rockstar has some legitimate beef with the PC platform, it seems to try so hard to avoid it if possible.