Others can purchase my old domain if I'm not renew it?

I have purchased several domains which are related to my blog. Specially org, net. Because of I don't like to see similar domains. I purchased them from Google apps ( enome and Godaddy).

I didn't renew them for this year. So anyone who interesting to that domain can purchase without my permission?

If you missed the "last chance to renew" emails then you just have to hope nobody will register them after the pending period is over and will be again available for register.