The creation (or abolition) of a legislative council in a state hinges primarily on that state's legislative assembly passing a resolution to create (or abolish) it. This however must be passed by the Parliament for the creation/abolition to be successful. To illustrate, in Article 169 of the Indian constitution states:
Parliament may by law provide for the abolition of the Legislative Council of a State having such a Council or for the creation of such a Council in a State having no such Council, if the Legislative Assembly
of the State passes a resolution to that effect by a majority of the total membership of the Assembly and by a majority of not less than two-thirds of the members of the Assembly present and voting.
Notice that the wording "may" is not binding and therefore the proposals for legislative councils in Rajasthan and Assam to be pending, as it has not gained traction amongst the members of the Rajya Sabha (and until that is achieved, the resolution is in suspended animation). Apparently the role and impact of legislative councils in general in Indian polity seems not to have lived up to the intended aim. The resolutions even went to a parliamentary committee but are still pending.
As for Telangana, since the state itself couldn't have passed a resolution since it didn't exist as per law. The parliament took upon its role to include the creation of the council within the ambit of the creation of the new state.
