If the mandated purchase is found to be unconstitutional, does that void the entire bill, or just those portions related to forced purchase?
Just the mandated purchase portion would be struck down.
There may be other suits later questioning portions of the insurance limitation provisions (requiring coverage for pre-existing conditions, for example) if it is found that an insurance company is operating solely within one state. No interstate commerce, no federal jurisdiction.
The rest of the bill and the reconciled changes will remain in force. Also look for a single payer system to be pushed when the mandatory purchase provisions are struck down. That, unfortunately, is constitutional, as demonstrated by Medicare and Medicaid.