Williamson averages 48.36 after 44 tests, dipping from his 49.26 peak in Perth last month after making 166 and 32 not out.
If he is dismissed four times in the two-test series against Sri Lanka, but scores 323 runs at 80.75 he will become the first New Zealand player to reach the mark beyond 32 tests.
Glenn Turner dipped to 48.65 after his 33rd test and ended up averaging 44.64 in 41.
At 25 years and 118 days old, Williamson consistently bats like he's a live geometry experiment.
Most shots appear measured and weighted to fit within the confines of an oval with the least number of hands or feet getting near them.
He finds the path of least resistance on attack and path of most resistance on defence. It seems inevitable he will break the hallowed 50 mark.
By the time Williamson turns 26, his 12 century tally will inevitably be closer aligned to Sachin Tendulkar (19), Sir Donald Bradman and Alastair Cook (15) and Sir Garfield Sobers (13) at the same age.
Ross Taylor is less likely to reach a 50 average this month, but he's still a possibility coming off a record innings of 290 for test players touring Australia.
He averages 46.61 in 67 tests and needs 576 runs at 144 in four completed innings against Sri Lanka to break the barrier.
Williamson might have the edge, so to speak, when it comes to technical finesse, but Taylor counters with a bat which is the equivalent of a bank vault door when his eye is in.
The pair have long been trumpeted as New Zealand's best test 3-4 combination and the series in Australia further compounded that hypothesis, particularly at Perth.
Their third-wicket stand of 265 was the highest by any New Zealand pair against Australia.
In 44 partnerships together, they average 58.15. That figure rises to 61.68 when it is for the third wicket.
Comparing their averages with others at their career peaks makes for curious - and some might argue skewed - reading.
New Zealand's highest average for those to have played more than 10 tests is John F Reid, who peaked at 58.50 after 12.
Turner, Andrew Jones, Mark Richardson, Jesse Ryder and Bert Sutcliffe had sustained periods averaging more than 50 before dropping later in their careers.
In contrast, Martin Crowe never got there, having endured the fury of Australia on debut in 1982. Stephen Fleming averaged 54 after his first test but never returned to those levels.
The quest for 50 adds further interest for a New Zealand public who are yet to see their side play a test at home since they were World Cup finalists. The opening Dunedin test starts Thursday.
