The home resort booking advantage (11 month window) only applies to points at that resort. If your new contract was for a different resort, you would not be able to combine at 11 months.
If your new contract has the same use year, you can seamlessly combine points to make a reservation. If they are the same home resort, you can combine at 11 months, and if they are different, then you can use them together at 7 months.
If you pick up a contract with a separate use year, they will be completely separate and you won't be able to combine points without transferring points from one to the other. Even still, transferred points retain their original home resort.