Re: How long until the new referendum will be called?
To be fair, there have been UKIP-ancestors longer than that. The National Front in the 1970s and the BNP since the 1980s campaigned for out, and their exclusion from all debate has probably fuelled some of the vitriol that now drives brexit.
What changed for UKIP (apart from deep-pocketed Establishment backing) was an era of white immigration, that helped a slick publicity machine separate an anti-immigration agenda from cries of racism that could've silenced them. Ironically they're basically right: anti-immigration and anti-immigrant are not the same, though there was ample overlap to see off the UKIP predecessors.