Re 16 weeks, I doubt it too! However, only so many people who had booked up at the beginning of the season will be able to exchange their dates for the back end, fair chance that there simply won't be the capacity available.
As for what exceptions can a yard make, exceptional times and I suspect that in typical, laid back Norfolk Broads style most yards will go the extra fathom or two but there has to be a reasonable limit as to what they can do. .
At best I suspect that we can expect little more than an eight week season, probably not even enough to cover running costs let alone make a profit.
I do wonder, and worry, as to how the small yards, forum member Andy at Freedom springs to mind, are going to cope.