10% discount has been offered to Second Hand S4, 0.3465$/Gh and shipping out within a week after full payment 
Expensive :p Though, it could potentially underclock to get really good efficiency. I really like the S4, but it's heavy, add in the shipping.. OMG... Not at the current BTC prices.
Are you guys releasing a new firmware for S4 that will support minerlink?
Potentially, yes.
Hopefully with an improved CGminer version so we don't have to update it manually every time an S4 dies? Would be nice if Antminer's interface also supported changing queue settings for us p2pool miners.