Is it a shooting star or an asteroid that will wipe out the dinosaur 'old' parties (leaving aside the fact that the Lib Dems have one of the longest histories of any party)? Much depends on the two remaining television debates which will be the defining events of the general election.
I think there will be some slippage as Lib Dem policies become widely known, but most voters are influenced by overall images rather than detailed proposals. However, much of the additional support will be retained. They seem to be doing particularly well among young people so if they can mobilise them to vote overall turnout could go up. It will also be boosted by the closeness of the contest.
The volcanic ash cloud has not contributed to Labour's reputation for competence. Naval aramads have turned out to be one ship and fleets of coaches have proved hard to organised. The Lib Dems could get more votes than them, but far fewer seats.