In reply to Pietrach:
They are central, and high, so if Scotland is generally cold enough for snow/ice, they will likely have it. They are proper mountains and you'd need proper kit. They are likely to keep remnants of snow cover if conditions have been cold enough in the recent past but warmed up when you are there. Beyond that, it just depends on the temperatures and precipitation that you get shortly before and when you are there. You either need to commit yourself and take what comes, or leave the decision to a few days before you go.