At 1M points it hardly makes a difference. Besides, 1 point -> 1 pixel mapping is good enough for a demo, but in practice it will produce nasty aliasing artifacts because real datasets aren't aligned with pixel coordinates. So you have to draw each point as a 2x2 square at least with precise shading, and we are back to the rasterizer pipeline. Edit: what actually needs to be computed is the integral of the points dataset over each square pixel, and that depends on the shape of each point, even if it's smaller than a pixel.

Aren't we at petaflops now with GPUs? 1M or even 1G points should be no issue if it renders to a framebuffer and doesn't go through mountains af JS framework rubbish followed by mountains of GTK/Qt/.NET rubbish.