it can mean 2 ways (more likely to happen):
1. the currently housing ward will be double mean 8 will become 16
2. the wards add in 2.38 will be double mean they will add 4 new wards

the thing Yoshida is vague because he spoil but hidden info at the same time; so dont get your hope up;dont assume anything is the best way to deal with ANY info being leak by Yoshi