This Homebrew tap allows you to install Qt4 (and various packages that depend on it) on macOS Sierra. You can install it like this:
brew tap lloydc99/qt4
brew tap-pin lloydc99/qt4
brew install qt
The installation may take a little while, since Qt4 will be recompiled from source.
Feel free to submit an issue or pull request if you run into any problems or have any suggestions for improvements to the packages.
Please note: Qt4 is unsupported by its creators, so there are likely security/usability problems with it that will never be resolved. If you can, please consider migrating your projects to Qt5.