I believe Jason47 said they have enough scripts written to last until the end of the year. Can't remember if that meant enough to tape shows until the end of the year, or if there are enough scripts to last until December (meaning taping through to May/2018).
Enough to tape episodes through December 2017. They are in October now. So, with 15 episodes taping every 2 weeks, that gives them about 8 weeks (60 episodes) they can tape during the WGA strike if it happens. Combining that with the many dark weeks and a possible long summer break, that should keep Days good with scripts until around September. If the strike is still going on in September, then they would have to turn to scab writers as they begin taping January 2018.