Of course the signature campaign will stop. Why would they keep paying money to advertise a service that doesn't exist anymore?
The campaign thread managed by Lauda is already locked. Some people reported that they received their payments this last few days. Not sure about the other users.
Lauda, she was worked exponential by managing this and tracking high number of people in SMAS list for forum's goodness. I personally, worry about Bitmixer's closing statement by team. They are one bestest bitcoin mixers who have been done great job. Cryptomixers and others wasn't compete it that much with them.
Could it be linked to BTC-e takedown and the arrest of the operator?
Main charge is money laundering, Bitmixer could be connected to BTC-e or even operated by the same people.
Remember one thing in Crypto world, anything is possible here. The great Satoshi Nakamoto may be my neighbour. Its sad to see Bitmixer go, because they were providing the best service in the market but its their decision and everyone has to agree with it. The signature campaign was running from a long long time and I think most of the participants will not be bothered about a week's payment.