Stolen iphone6 What Now?

My iphone6 was stolen and I had a passcode on it. Apparently they got around that since I saw some incoming and outgoing calls after the date it was stolen. I tracked it until my new phone came in and was activated. ATT blacklisted the imei, but here's my question...

I had not gone into icloud and erased the phone before ATT blacklisted the imei. So are the people who have the phone still able to get into it and read my emails offline? And...if they do get near wifi, and power up the phone, will it actually connect and the erase request kick in?

Thanks for your help.