I just recently traveled from Mumbai to Chennai by 3rd class AC. My sister booked tickets for me in the last minute by Tatkal and it was waiting list WL2 and WL3.

The waiting list status is mostly updated only when chart is prepared for the train. Some seats (Quota's and so on) are released and waiting list has a possibility to get confirmed.

Booking is stopped 4 hours before departure of a train and chart preparation takes some time. So, Chart data is uploaded to online IRCTC site between 2 to 3 hours before departure of the train.

In my case, the chart was available 2:30 hours before departure and my ticket was confirmed.

Some of the useful tools are to SMS "PNR " to 139 to check status.