Honestly, I suspect RAAus is having a much bigger impact than the ASIC card. Gliding has seen the same sort of numbers drop as GA, but for a few more years now. I suspect that's because RAAus operators started appearing as far away from the CBD as the gliding operators, but in the past two years a lot of flying schools have started adding LSA's to their fleet as well.
It sucked up a lot of potential glider pilots - why would you want to spend all day on an airfield for half hour of flying when you can pay for your time slot in an Ultralight that really isn't that much more expensive. Now we're starting to see it in GA as well - why would you spend twice as much flying a 1970 C172 when for half the price you can hire a near new Sportstar, Jabiru, Texan, Sport Cub or Lightwing - especially now the aircraft is 30mins from home at the local GAAP as opposed to 1.5hrs away at the local gliding club?
There'll be a decline in the number of PPL holders, but these people were never really after a PPL anyway - they just wanted the freedom to go flying and occasionally take a friend up. The number of CPL holders won't change too dramatically - there's a lot of people starting in the RAAus with the intention of getting a CPL eventually.
That said the ASIC is the biggest WOFTAM I know of.