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 &amp; 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