While I too, like the Vikings, more castle themes wouldn't hurt. ;)
Where I think it will head? It looks to me TLC is just going to keep going with KK2 :(
Where I think it should go? I like your idea for Middle-Eastern Knights, that would be cool. Something like 'Merry old England' or something would also be cool; they could make different houses and workshops and things, with lots of town folk. :') They could also make more Forestmen... I always liked the forestmen. They could also make different factions, and give them little outposts and things, maybe a castle or two... Maybe a dock, and medieval pirates...
There are lots of possible things TLC could do with a theme like that.
I know it will probably never happen, but I can dream right?