The potential in parliamentary terms is clear: what seems to me to be by far the most likely option would be that Cameron would be forced to stand down immediately if Exit wins, and faced with with the task of delivering the Exit Johnson would be favourite to take the job (bookies agree), and there's already been talk of Farage taking a future cabinet position. Certainly a UKIP/Tory coalition could be a possibility should the need arise.
But lets say that doesnt happen. There are two further options - Torys continuing to hold power with Cameron or more likely another non-Johnson successor, or a Labour government under Corbyn. In both those scenarios Johnson and Farage are both now positioned as the true voice of Exit, and their political careers are firmly pinned to it. Even if the referendum goes to Exit there will still be a long fight to be had to push it through in a way that satisfies Johnson and Farage and their supporters, and they will have the political capital and 'moral authority' to set the agenda and berate anyone who strays from the path. It is their vision of Exit that is being voted for, not a leftist one. They will be justified to say that the British voting public are being ignored, and that their will is not being exercised, and undermine the authority of whoever else might be in power, Tory or Labour. Cue even more pandering to the UKIP agenda.
A vote for Exit would be the very beginning of years of power politics over what form the New UK might take (and there are many potential versions), and there's no way Johnson and Farage are going to go into retirement post-vote, job done - the opposite - this will be the beginning of their real chance at power, by hook or crook ( but most likely by a quick takeover from Cameron).
I was for Scottish independence, partly because I felt the SNP agenda was a safe way in which to implement it. If it had been a Scottish UKIP calling for Scottish Independence, producing racist posters etc and ready to take power, I wouldnt have supported it. Neither Scottish Exit or UK Exit is a neutral political act; the manner and power behind the process is not just mood music - I think it will profoundly shape the politics of the short and mid term.
To my mind voting for Exit isnt just voting for something that happens to have Farage and Johnson representing it, to which its possible to hold your nose because once it passes there's a post-EU carte blanche to play for - I believe in realpolitik terms it will be a direct vote for them and their agenda. It will empower them and put them centre stage for years to come.