On top of my wishlist, of course, some missing animals:
Bats (Whats the problem about that? They released the fourth generation of castles last year, there was a goldmine in the western theme, the jungle theme and even a dracula-special but not one small, single bat. I think there is a bat-hater at the development department...)
Lamas (I hope there'll be one when they relaunch the circus theme...)
...a walrus, otters, piranhas, lynx, snow leopard, polar fox and an anteater. I think that would complete the "premier league" of animals that are more or less popular to most people.
There were some really nice ideas in this thread, especially that cloud-baseplates would be something completely new but it might be too abstract for the people at geobra. The amusement-park is sure one of the top wishes from adult playmofans but there was an statement from geobra last year that they'll not realise it because the sets would be far too expensive and the play-value for the target group would be to small. Maybe this could be a target for the collectors-club one day...Lego shows with this giant star-wars-sets that there is a market for such things.
Some other things i would like to see: ice-age theme, a beekeeper-special, an anthill for the forest theme, a paraglider, a hang-glider, a hot air balloon and an airship (zeppelin) *dreaming*