To be completely honest, there are so many unknowns with your post that it’s impossible to give an accurate estimation of time/cost. How skilled are your programmers (2 great programmers can run circles around 4 moderately decent ones)? How much direction have you given for your project (ex: will your programmer know exactly what to implement and how long YOU expect it to take to finish…and not the other way around)? How much time do you plan on devoting to testing/bug fixes (trust me…they’ll happen no matter how good your programmer are)? What’s your budget (time & money)?
A general rule of thumb when it comes to project time/cost estimations: Cost = Complexity x Time x Artists/Programmers x Skill. It’s really not an official formula, but hopefully you get the picture…costs can add up quickly. You can hire decent programmers but your timeline gets extended, versus hiring skilled (more expensive) programmers and saving time on development. If you have little to no direction for the project, your deadlines just got really extended!
But…to answer your question with the information you’ve posted…I’d venture to say you could expect your game to be developed anywhere from 3-12 months depending on complexity and the skills of your programmers.