What ? Akatsuki can't have spys ? lolHow???
Tobi is not sending Sasuke to capture 8-tails because Kisame is up to it . And Tobi said himself : " ...but I don't care about him anymore ...there's something else I want you to do "ok good was not sure . but why tobi is sending sasuke and half of zensu to go and take on 5 hokages and their bodyguards .. and not sending him to go capture naruto .know that akatsuki is in a weak state or send him to capture the 8 tails again
Tobi wants Sasuke to kill Kages or atleast make chaos there , so it's more important than 9-tails for him now .