HMS DUNCAN launch

How many more years until the next new ship appears in Govan?

Quite a while I would think. The current construction is on the carrier blocks which will go onto a barge I believe to be taken round to Rosyth depending of course on the Defence Review. The Clyde yards are doing the design work for the Type 22/23 replacements but who knows when they will appear....
The Govan fitting out basin is probably going to be converted to a building dock providing of course that the yard remains open!

yes normally launches are accmpanied by promises of new orders, but that fell foul when Daring was launched and Ships 7 and 8 were hinted at

Yes, they were for export supposedly.

i remember the initial plan for 12 with Daring built at Scotstoun and the rest assembled and dunked on the ship lift at Barrow-in-furness