Due to a settlement in Jan 2001, MS are phasing out a whole bunch of products including IE5.5, you can get the complete list of products here. As a part of the settlement aswell they also have to make some of there other products Java compliant.
Back to the IE5.5 issue though. Personally i dont mind the browser or coding for it. But soon its going to be gone in replacment of IE6. Also (i'm thinking out loud now), are MS going to push all users to IE 6, mainly because of the Eolas case back in August. You see, where in the past most people could choose more freely there upgrade path (we still download IE5.5 here for some machines), surely now MS have to been seen to be pushing their users to a new compliant browser, and even prevent them from downloading/obtaining older versions? "If" they do, then its good news for us, i mean the more browsers on the same version number the better.
Though no doubt IE5.5 will survive, along with IE5.1 aswell as NS6.1 and dare i say it NS4.5. You never know maybe one day the developer dreams of all browser being fully compliant and acting in the same way will come true.