This thread got me curious so I went and looked at the Steamcharts for this game.
The frist month it was out it averaged around 4k players which isn't great but not terrible. The following month it dropped to a little over 1700, which is pretty bad. The next month, which is when it was rumored that it was done, it dropped to 800. The numbers obviously fall off a cliff after that.
We can assume that most of the open beta players stayed on the stand alone client just for ease of use so I'd say we can up those averages by around 500-1000. Not a huge bump but a bump none the less.
What makes this really interesting is looking at a similar situation in Gotham City Imposters, which to this day is playable on Steam. Imposters averaged 2100 in it's opening month before falling to an astounding 940 the next month. The month after that it falls to 694 and every month after that for about 2 years it hovers around 300 players. Fast forward to today and it averages 15 players a month, with 11 online right now.
I guess my question is why did DC pull the plug on Infinite Crisis so fast when they have another free to play multiplayer game that lost popularity faster still running today. Seems very strange to me.