You might want to proofread your posts before posting, there's a couple of pretty obvious spelling errors in your post. Most browsers also offer either a built-in spelling checker or have one available as a plug-in.
It defiently looked like C'Thun is not fully gone. Cho'gall even mentions resurecting his master. At the end of the issue he draws on his master's power and his amrs goo all huge and look like something that could have popped right off of C'Thun. It's pretty unmistakable, as he is shown off in the last pannel glaring down at Valeera.
This could explain Yogg Sarron's reaction to getting "killed", it knows that such a thing really will not be an impediment.
What if this is the main reason why killing the Old Gods involves them being able to do something really bad in spirt form? Maybe along the lines that to make a new body they would ahve to devour the host? The more that get killed, the fast the process advances.