Commitment comes from within and develops with time not from a conversation. If you feel that you should become more serious and take it a step farther, think why it hasn't happened yet. Usually both partners commit almost in a parallel way, since they feed their relationship together and grow as individuals and as a couple. If you think the conversation is necessary, then don't be afraid. Say things the way they are and how you feel them, If your partner changes attitude towards you because he felt pressured it means you should reconsider your relationship. If you don't mind him being less committed than you, then keep working on your relationship. It's really up to you, and how you feel about it, but never forget to take into consideration your significant other's feelings and opinions.