[jamesfinlayson]

I think GitHub at least is spinning off parts (not sure about Shopify) but as others are getting at, rewriting a big, business critical application is risky.

I worked at a place that was completely rewriting a PHP site in PHP (moving from a no framework no test spaghetti code base to something structured and tested) and that was a six year project just to get feature parity with the old site. During four of those years features were being added to both sites in parallel too which doubled the cost of every feature.