We have built a composer package that allows you to use twig templates within concrete5:
https://github.com/mainio/c5pkg_twig_templates...
It is used for example by this example package that also integrates with the Symfony forms package:
https://github.com/mainio/c5_symfony_forms_example...
It currently allows you to build any controller handled views with the twig templates. What is missing is possibility to also use it within the themes and page type templates. If you need these features, just make some noise in the GitHub issues of that pacakge.
You can also maybe make this issue a higher priority in the eyes of the core team by adding a comment in the first GitHub issue above linked by @MrKDilkington.
https://github.com/mainio/c5pkg_twig_templates...
It is used for example by this example package that also integrates with the Symfony forms package:
https://github.com/mainio/c5_symfony_forms_example...
It currently allows you to build any controller handled views with the twig templates. What is missing is possibility to also use it within the themes and page type templates. If you need these features, just make some noise in the GitHub issues of that pacakge.
You can also maybe make this issue a higher priority in the eyes of the core team by adding a comment in the first GitHub issue above linked by @MrKDilkington.
I am not aware of any plans to use Twig templates, but there is a discussion and a package you can look at.
"Symfony forms integration #2717"
https://github.com/concrete5/concrete5/issues/2717...
This package uses Twig and Composer:
https://github.com/Buttress/addon_composer_sample...