Automatic, always-on per-layout memory loading was implemented in r107. However, it only affects the WebGL renderer, because the canvas 2D API does not provide manual memory management. For browsers which do not support WebGL (notably IE10/Win8) it's simply up to the browser to manage memory intelligently. It's possible it does this already, but it's hard to test - your best best is to ask the browser vendor. On CocoonJS and directCanvas it's also not supported, but it may be coming soon (I've discussed with both about implementing it explicity even though they're both currently canvas 2D rendered).
Edit: Arima ninja'd