Can we really call Oliver's identity a secret anymore? It seems that half of Starling City know who the Arrow really is... and that number is about to go up by two. According to the PaleyFest panel, Ray Palmer and Detective Lance are about to discover Oliver's secret - essentially making every major character in the show aware of what is going on.
It's unsurprising that Ray would find out, now that his ATOM suit is up and running and he's going to be taking to the streets as a vigilante himself. Executive Producer Marc Guggenheim revealed to TVLine that although Palmer may have a similar goal to Arrow, they are definitely not working together to achieve it. [Ray will] go about things in a very different way than the Arrow does and he's not a part of Team Arrow. Right now, he's just a very smart guy in a very, very powerful suit.
Oliver's definitely going to have an opinion, and the first instance of that will be in Episode 317. As for Detective Lance, well it's about time!! He's been working with Arrow for some time now, but he hasn't yet discovered his true identity. Now he'll find out, and it seems that he isn't too happy about it.