Poloniex is my first exchange.Well that they have updates,but I think that their time has passed.In my opinion Bitmax is the leader of margin trading.Although as they say never say never.Perhaps the management of the exchange will be able to somehow attract the target audience.
Most new companies you see thriving today is not because they have any special idea, what they are doing is just to simply build on already existing ones, but making it better by looking for problems they are yet to find solution to,
You cannot completely conclude that their time has passed, bitmax might be doing great now, but they will still have a particular problem they are yet to find solution to and that is what poloniex will probably use, by looking for a way to solve such problem and add it as additional feature to the already great features they have that will announce them above every other exchanges.