It is a difficult question with very simple answer. As long as your career and financial goals are met you want to keep working with a company. This is not the time to tell your personal situation about when do you want to quit company or move to a different city. Do not give any extra information that is not yet confirmed.
Sample answer is:
My long-term career goal is to be an Architect in software development. I see that your organization has very good product line and technology stack to grow my career here. I would like to develop my career here to reach my long-term career goals.