UKIP can't become a big party in the sense that FPTP ****s up any possibility of UKIP winning seats. But i do think that the UKIP vote will keep getting higher and higher and so the Tories will find it more difficult to win majority's in parliament. This i think will force a future Tory Govt. into calling for an EU referendum, otherwise Labour will start to find elections very easy to win.
I expect UKIP will profit immensely from Cameron's traitorous decision to quash a referendum on the EU, my prediction is that they'll come first in the 2014 European Parliament election and continue to snap at the heels of the big 3 during all the by-elections and local elections between now and the next general election.
I think personally what they should instead do is to concentrate on a regional area rather than be a nationwide party. That way it could concentrate its resources and stay focused in winning a few winnable seats rather than spreading itself thin and just being merely a party that removes votes from the Conservatives.
One thing for sure, they would definitely need to rebrand and reinvent themselves to be more than just a single issue party that it is now perceived to be.
I must say after living, working and doing business in Switzerland I think the UKIP is exactly that UK needs.