According to Forex Magnates (and Yohay at forexcrunch.com) who cite persons with knowledge of the deal.

So far that makes Iron FX and Oanda as the two front runners.

The likely scenario is that these firms just want the client books of Alpari rather than taking up the business lock stock. We’ll have to see what deal is struck but if any potential buyers deems the sums worthwhile it could mean that they let off any negative balances to keep hold of those customers. That’s just pure speculation on my part though. The administrators will be looking to either re-coop the losses or sell them off.