No, there is no need for new consideration once your current contract is up. Remember: employment in this country is "employment at will" except when you are under a still-in-effect (unexpired) employment contract. Once the contract expires, therefore, you are that point an employe at will and could be terminated (or anything less than termination: e.g. demoted) if the employer wants and have no guaranty of employment. Therefore, just letting you keep your job would be enough consideration for a renewal of the contract, since they don't have to do that.