I am sorry, let me clarify your question

If your I-485 is based on your approved I-140, the approval rate is quite optimistic, that means your I-485 will be mostly approved too; however, if you I-485 is based on concurrent filling with I-140, that depends on your I-140, and the chance may not as optimistic as the above one. I hope my misinformation above does not scare you too much because I did not read carefully and thought that was I-140. As to I-485 I believe over 90% will be approved. Again, apologize for my negligence.