So what will be their edge now? Definitely not their platform b/c nobody cares. Their presumably low fees were always their sales pitch.market making is a dying business. Markets are sufficiently efficient enough to not necessitate market makers. In the same way as specialists were never necessary, nor floor brokers. As long as there is a market place where supply can meet demand then that is all one needs.
By the way, IB's Peterffy stated this exit himself in one of the more recent conf calls.