I doubt they will have enough support to gain any MPs.
It's most likely that their vote will collapse for a real election.
(Fingers crossed).
Still, UKIP success is our best chance of avoiding another Tory government, so it's swings and roundabouts I suppose
UKIP will almost certainly pick up MP's in 2015, they have seen a strong growth over the last few years and could well have 17-20% of the national vote by 2015 (polling at around 11-15% now IIRC), how many seats that will actually translate into I don't know. We could end up with a hung parliament with UKIP holding the balance of power (A Tory-UKIP coalition being a often discussed idea) or UKIP not really having an influence, but I'm almost certain they will get MP's.
Something interesting to come out of the last few weeks is that UKIP seems to be utterly immune to the scathing media attacks they have been subjected to. While the mainstream media has done everything possible to attack the party, they are up in the polls and look certain to come top in the EU elections. Personally I think the media is going down the wrong road, it's clear to anyone who has done their research that UKIP isn't a racist party, at least their policy isn't, so using that as a stick to beat them with doesn't deter their current support and actually makes others who held that view go and look them up and come to the that conclusiom. It worked well when UKIP were a small fringe party, who had some radical right elements, but against 2014's cleaned up UKIP it just isn't working, how can you play the racist card when UKIP has plenty of ethnic minority candidates and members? It just doesn't work.
If the left really wanted to get at UKIP they should be going after policy/economics, UKIP is actually picking up a fair bit of old Labour vote who don't feel represented by Labour anymore and see UKIP as a protest vote or want a referendum on the EU but would never vote Tory (who won't give them one anyway) Their target should be the lack of any major policy outside of the EU and their libertarian ideals, which could easily be conflated with Thatcher, making Frottage out as a "new Thatcher, enemy of the working man" would be a much stronger attack, even if it isn't really true. The worst that could happen is splitting the right wing vote. At the moment it's UKIP talking about "taking on the establishment" and a "peoples army", which is the right move for them and attracts people disillusioned with the current political system.