Traditionally, as I understand it the British parliament sits on annual sessions. Each one starting with a Queen's speech. After an election winning a vote on a Queen's speech is requirement for an incoming government.
In 2017 a decision was taken to have a 2 year session to encompass leaving the EU. This was seen as unusual but not exceptional.
The two years are almost up. However, there is suggestion that the government will not put forward another Queen's speech and just prolong this session of parliament (see https://www.theguardian.com/politics/2019/apr/17/theresa-may-could-put-off-queens-speech-amid-brexit-turmoil)
It is suggested this would cause "constitutional outrage", but that is not uncommon in the UK currently.
Other than mechanisms under the fixed term parliament act, a vote of no confidence or a scheduled election, is there an way for parliament to end its own session and demand a new Queen's speech? Or is it possible for the government to just carry on without an agenda indefinitely?