Do the writers have more than a five year plan?

So far, each season of Arrow has corresponded to roughly one year of time during Oliver's time away from Starling City, each five years previous to the "current" year.

Given the current pattern, season 6 would run past the available flashback years.

Have producers/writers stated whether or not they have a plan to address this issue?

No, I'm not expecting a quote on a detailed plan - I'm just hoping for some sort of statement on whether not long term plans past season 5 exist or have been considered.