I just read the chapter and I agree. The other clone Misaki is talking about seems to likely be Misaka #00000-Full Tuning...
It was a bit underwhelming of a chapter (not to say that it wasn't good) but it was a necessary one to finally begin tying up loose ends. Seems like the arc will be ending in the next couple of chapters (whether it's one or three is still unclear but I personally estimate 1-2 more chapters left).
On another note, I love how Mitori just scrolls past the all important info about Parameter List without even batting an eye. Had she kept that info...she could have succeeded in destroying Academy City in another way. The upheaval she could have caused within Academy City if she released that info would be incredible.