You are right that there is a hole where there used to be a large ship ... Perhaps, just perhaps ... 3940 will be released as a Classic? It has happened to the Schooner ...
Without a DECENT ship, pirates become just landrats and have no reason for existance.
3940 (= 3286 for USA) as a Classic Edition? Hmm...
Perhaps without klickies and accessories and canons, otherwise I think it would be very expensive for a Direct Service set...
The 6678 is still available. Maybe they're taking a step back from the pirate theme to rethink it and maybe they are planning something new for next year.
Sales must be an influence as well. Is the theme selling as well as it used to or are kids less interested by pirates now that there's no new Disney pirate movie?
Yes, 6678 is still available, but when it is not mentioned/shown anymore in the German catalogue, I think that means they´re just selling out their stock. And the US & other foreign countries´ catalogues run always 1 year behind the German & Benelux-countries ones, discontinued sets are 1 year longer available outside the "home" market (and usually sets & themes are also realeased 1 year later on the "foreign" markets).
Also, 6678 is a very dumbed down big ship; it comes without cabin, with a tiny cargo-hold, with stickers as fake-cabinwindows, very fake stick-on canonports, etc.
Sales of that one will probably be WAY down when compared with the sales of it´s predecessor-ships.
Myself for instance, I bought more then a "dirty dozen" of the 3940-flagship released in 2000 and also of the 5135-variant released in 2011. What the silly 6678 is concerned, I bought ... just 1. So sales are certainly down in my area!
I always hoped there would come a sequel to the movie "Master & Commander - The Far Side of The World" with Russel Crow, the end of the film left an opening to a sequel and there were some rumours once, but it never materialised...