1. How old are you? where are you in career? How much financially do you need to keep this particular job?
2. Is your skill very marketable?
3. Is your compensation at current position at/below/above market rate(your unique knowlege at current job might earn you a premium but not transferrable to another job)?
4. If Bill can easily lead the project, does that mean you don't have much to offer? Take it as a lesson in your next job, always build your competative advantage, either by the right way(always lead) or the wrong way(build a wall to guard your status).
5. Since there is a prototype, can you get to know it and become really good at it?