Prime Minister Lee Hsien Loong recently announced that the Electoral Boundaries Review Committee (EBRC) was formed two months back. The EBRC will draw up election boundaries, which, going by the most recent elections, will likely take another two months. Polling has historically occurred between 17 days and six months after the boundaries are drawn, so there is some uncertainty over when elections will be.
The number of days between the two events - drawing the boundaries and elections - averaged 43 days since the 1991 elections, and ranged between 17 to 71 days. Using this information, I calculated the probability that elections would occur by a certain date. The results are summarised in the chart below.
Elections are unlikely to occur in the first week of October (also considering that it is the PSLE examination week), but has half a chance of occurring by 28 October. The cumulative probability is practically 100% by 1st Jan, hence elections are quite certainly going to occur within the year.
However, given that the O levels examinations only conclude in 13 November, my guess is that elections will occur in the 2nd half of November.
Lastly, this is premised on the EBRC report being released on 14 Sep 2015, so I will update again once the final report is released.