Twitter will remove inactive users from 11 December. For that reason, a number of older usernames will probably be released long term.
Twitter points out that it will gradually get rid of inactive profiles. As a result, their tweets also disappear, and they also no more add up as fans along with other profiles.
For profiles of deceased persons, the company is considering a sort of Memoriam in which the tweets of that particular person could be saved, but just how exactly that will continue to work is not really yet very clear.
As profiles are cleaned up, the consumer brands of these accounts can also be introduced. When that occurs effectively is not known. The Verge information that all mixtures with five letters have been consumed nowadays, a number of them could be launched in the long run.