I can't see Clinton actually quitting. She will probably acknowledge that Obama seems to have secured the nomination but she will continue to campaign. Financially she is in an awkward position and like a shark she really can't stop swimming or she will drown. It will be more conciliatory and aimed more at strengthening the Democratic ticket but I think we will see an end to her attacks on Obama.
Clinton needs to recover and rebuild her brand. I think she will emerge from this race for the nomination a different politician than she was before. I have no idea if that will be for better or for worse but I expect she will change something fundamental about how she practices politics. In a totally unnoticed diary I explained my opinion she was most likely carried astray by her hopes and fears. I've often found that to be a good explanation for seemingly irrational behavior.
Clinton has been brought back to reality now (crosses fingers) so I look forward to seeing how she reinvents herself this time and how she intends to help Democratic candidates going forward.