You can programmatically zoom / pan to a region by setting viewportMinimum and viewportMaximum. In your case, you can set viewportMaximum to null (which resets the viewportMaximum) when user has zoomed / panned towards the latest dataPoint (latest part of the chart) using rangeChanged event. Please take a look at this JSFiddle.
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Vishwas R
Team CanvasJS