Assuming 1.5 releases within the next few weeks, that'll be 5 updates over the course of 13 months. Averaged that's an update every 2.6 months. Each update accomplished something, especially 1.2.5 (increased height and jungle biomes) and 1.3 (the merge). 1.5 is coming along to fix the lighting bugs and polish up redstone.
I agree that Mojang does seemingly work slow on content compared to many modders, but considering I get these updates for free I'm in no position to complain.
Mojang is not getting lazy.
Coding things into the game properly can take a lot of thinking and problem solving. Mojang has been primarily fixing bugs within the past few updates, which I'm sure is a challenge of its own degree. You just have to understand that adding too many features and not fixing enough bugs would be a very bad thing.
"Everything in moderation"...
They aren't lazy, i personally feel a lack of single-player content lately. If you are a "noob" player there really isn't anything good in the upcoming update. They need to add more player items and what-not.
Do you expect Mojang to be a super fast cyborg that can add 2000 features in 50 minutes? The Mojang Team are just like us, human. They need a rest. Also do you know how much time they had to code? Can you run a company that can make good quality features within 2 minutes? Always remember, Quality is more important than Quantity.