Spoiler alert from the preview:
They showed a guy getting knifed in a prison.
I didn't watch that preview until now. It didn't show who used the knife, so I think they may be trying to mislead the viewers into thinking that Walt will order Fring's men killed.
When you actually think about it, how would Walt order the simultaneous killing of multiple men in prison? It would be extraordinarily difficult to be able to systematically kill them off without one of them realizing what's happening and deciding to talk for protection.
It could be that one of Fring's men voluntarily kills the one guy who offers to talk to the DEA as a sign of loyalty to Walt in hopes that they continue being paid.
I also noticed in the preview that Lydia is putting meth into a barrel, presumably at her business. I am assuming that the DEA bugs are still on a barrel (or barrels), so Walt may be attempting to use those bugged barrels in order to frame someone else. Once he's in the clear and can churn out his product without worry (at least in his mind), he'd be able to easily pay the remainder of the hush money.
Afterall, Mike was going to keep paying off those guys once he received a one-time payment of $5 million for his share of the methylamine. The lawyer was putting $15,000 in each safe deposit box during each visit. If Walt can turn 1,000 gallons of methylamine into $100 million, then he would have no problems paying those guys off, and thus shouldn't have to worry about trying to have 9 people killed in prison at once.