The comparison to PHP5 is definitely interesting. PHP5 was released around 2004 with significant upgrades to the language with a high degree of backwards-compatibility and it still hasn't reached complete adoption. Only now with official support coming to an end and more web host support, will it become the standard.
The adoption of Python 3 will likely differ, since Python is not a standard feature of low-cost web hosts and has a wide range of uses outside of web development. It should be interesting to see how this plays out.
The adoption of Python 3 will likely differ, since Python is not a standard feature of low-cost web hosts and has a wide range of uses outside of web development. It should be interesting to see how this plays out.