When tjalorak mentioned Kokushi-Musou, I counted Saki's discards and it looks like there are 7 (Kana had 8th when she throwed away Suanko), which is exactly number of tiles what she need to change, coincidence? Maybe
Personally I prefer to already finish it, because it's way too looong and if author decide to prolong it again by some bonus rounds anime will cover it first
Btw what exactly means 13 sided wait in case of Kokushi-Musou? To have all terminals/dragons/winds prepared and waiting for pair?