That's an interesting thought for sure. But consider that with an advent of golang, node.js and other faster (compared to python and ruby) languages/frameworks

That's an interesting thought for sure. But consider that with an advent of golang, node.js and other faster (compared to python and ruby) languages/frameworks coupled with microservices architecture most (maybe 80%) startups will not exceed 10 or 15 free dynos. Those who need vertical scaling may pay for 2 or 3 dyno workers. Where's the scalable business model for Heroku in this scenario? So I am not sure that Heroku wants startups to migrate.