Our daughter attended a play-based co-op preschool for only one year (the year right before kindergarten), and she did very well academically in kindergarten. She also continues to do well in first grade, both in her studies and in socializing with other kids. For her, one year of preschool was enough.

As you make the decision for your child, here are some Education.com resources you may find helpful...

The Parents Guide to Preschool
http://www.education.com/grade/preschool/

Kindergarten Readiness
http://www.education.com/topic/kindergarten-readiness/  

All the best to you and your family as you continue reading, playing and exploring in the years before kindergarten (and beyond).

Contact the school that you are planning for your child to attend, they should be able to provide you with a list of expectations for students entering kindergarten.  My sister taught kindergarten 3 years, before moving on to first then second grade, she said children enter will all  types of abilities, but are most successful when they are socially  mature and excited about learning.  Many schools have entrance exams that allow the curriculum director to place students in integrated classrooms, meaning not all the students that are advanced are in one classroom. Children learn from one another more quickly than we give them credit for doing. (sometimes  that is not a positive thing, my son learned not all kids had to say please and thank you)  Good luck

The answer to your question depends on a great deal of things. This link addresses several things to consider:  http://www.education.com/reference/article/Ref_Preparing_Your_Child/
Best of luck!