Just checking today that there's no new info about winter moorings, I googled 'rct winter moorings 2019 faq' and followed links to a RCT pdf titled '38663-2019-20-winter-mooring-frequently-asked-questions-faqs.pdf' which it turned out was possibly a re-titled copy of last years i.e. 2018-2019.
While the file name said '-2019-2020-', the document was named 'winter moorings 2018/19' and though page 2 said sales start 3rd October, page 4 said 'moorings available from Monday 1 Oct.'
All a bit confusing so I rang up RCT to be told it was 'almost certainly Thurs, 3 October'.
So, if you're keen on a particular booking, you might want to keep an eye on boths dates - just in case.