Drupal - Will Lime the future test suite?

Not sure about Lime, but Drupal 8 is set to use PHPUnit. See Deploy a PHPUnit system with a bottom-up approach.

Deploy a PHPUnit system with a bottom-up approach

Issue Summary

Replace the SimpleTest framework with PHPUnit.

Problem/Motivations

The SimpleTest framework no longer has the same level of maintenance than the PHP Unit framework. PHPUnit has become the standard; most frameworks use it (ZF1 & 2, Cake, Symfony2, ...) and is actively maintained, sable and works great for every codebase, scenario.

Replacing the testing framework with PHPUnit will allow better consistency in the drupal 8 codebase, by aligning ourselves with Symfony2 testing tools. Moreover, it integrates better with IDE (NetBeans, Eclipse, IntelliJ IDEA), Continuous Integration servers such as Jenkins/Hudson, and with Sonar for static code analysis as well. It has also code coverage which is a huge +.

EDIT

Following the comment from chx below about me posting the wrong issue, I'm pretty sure that this is the issue that noted the progress of PHPUnit: Start using PHPUnit for unit tests

You linked the Symfony 1 documentation, which shows this warning.

This version of Symfony is not maintained anymore. If some of your projects still use this version, consider upgrading.

The relevant link is the Testing chapter in the Symfony 2 book. Both Symfony 2 and Drupal 8 is using PHPunit although Drupal 8 didn't throw out the massive amount of functional tests written with our bastardized version of Simpletest. You can clone Drupal and in the core directory just run phpunit (if you have installed it already). Alternatively, enable the Testing module and then you can run the PHPunit tests from that UI.