Not that I would put anything past this dumb show, but I don't think Oliver's going to be fighting crime in Star City like nothing's changed. Last episode, Felicity had her little chat with Alena about going off line to keep Mia safe, and Oliver had his little dream quest with Tommy about ending his cycle of violence. They seem to be setting up the team breaking up in some way (the Mark of 4 tattoos and promise, no one on the team but Diggle knowing about Mia, etc.) - even the title of the final episode indicates an endpoint of the vigilantes as we know them in Star City.
If Oliver does wind up fighting crime in Star City without Felicity, I hope the reasoning is sound. If not? Eh. This show doesn't make the best decisions, but I'd personally rather it make the bad decision where they're still together (and seeing each other occasionally/off screen) vs. not.