It seems that David Cameron has declared he does not want his Conservative party to form another coalition after the next election and would go into minority government instead, according to a report in the Telegraph
Tories are the senior partners in a coalition government with the
Liberal Democrats but will fight next May’s general election on a
promise not to form another coalition in the event of a hung parliament,
The Telegraph claim that an expected that a minority government would soon collapse, triggering a second election.
Except of course we have fixed term parliaments now and the public might just say to all parties we've voted its up to you to sought it out.
Of course it may depend on how far they are away from a majority
If Labour need to form a coalition with more than one party then just as happened in Wales and Scotland they could carry on making agreements on a Bil by Bill Basis
a compromise with the Unionist Parties in A compromise solution will not take take the Conservative whip but
vote with them on national issues and will vote independently on issues
relating to Northern Ireland
With fixed term Parliaments David Cameron would have to lose a vote of confidence though that again does not bind him to resign and "Go to the Queen" who is the only person who can really call an election and she might simply say carry on.
After the next General Election the Queen calls David Cameron who is still Prime Minister and ask him if he could form a government if he can't . She then calls Ed Miliband and if he can't she can in theory call anyone even a member of the House of Lords (Who is a Member of Parliament in a different House). Its been a while since the PM was a Lord but there,s nothing barring this.
Conservative MPs may force a leadership contest and elect one more wiling to enter a coalition.
The point is that there's no written constitution on this
In theory if say if Plaid's Jonathan Edwards was able to get backing from MPs he could go to the Queen and say he can form a government .
There's of course a 0.01% of this happening but there's no constitutional reason why it can't.
The point is that if Cameron who is responsible for fixed term parliament wants to can carry on without a majority . He could if the polls are with him call for a confidence vote himself and deliberately lose it
If theres a hung Parliament in 2015 there no reason why it shouldn't last 5 years and thats how it should be.