Based on the timeline you provided, you can extend your H-1B for the 7th-year. Ask around to make sure the timeline is right. Even your employer can not make the applcation in two month, I do not think the difference from a year is significant. Is it possible for you to taka a vacation in China for that amount time? Or have you ever took a long vacation in China (you may need airtiket,boarding pass as evidence)? If that is case, you can later claim that amount of time when applying for an extension. This strategy will work in case perm or 140 takes extra long processing time.