One area to consider is the design of your product. You may wish to use a technical architect to advise on how to make the product as open to future development as possible, both in terms of the code being developed and the design of any underpinning data structures.
You should also maintain market awareness of what your competitor products are doing, if you can, and prioritising your developments accordingly. Keep flexible: if a new idea brings more value than something that you are working on, then consider putting current developments on hold to let you progress the new bits (but beware of chasing every new idea and never implementing anything!)
Although you are the project manager, you should not be expected to be the only person managing the flow of ideas. You will presumably have access to the rest of the company, and your sales and marketing people will be key stakeholder groups. Use them to help you to keep aware of what is important and what will give them a cutting edge. Get them into your project as formal members of the team!