I think Wordpress can change whatever they want whenever they want, because it's free. Typically when they change something, they leave the depreciated command(s) in as well -- they try really hard NOT to break things.

And, being completely open source and written in PHP, if they take something out that you miss, you can always go put it back in.

1. I think there was a message here about how some function in Wordpress was changed, breaking code that ran using it because the arguments were no longer the same. Here's a reference to an article about SAAS where if you're using it, your vendor can change your contract interfaces and some don't even tell you when they do so: http://www.infoworld.com/d/adventures-in-it/little-bit-cloud-computing-goes-long-way-374?page=0,0&source=IFWNLE_nlt_blogs_2010-11-18

2. Wordpress provides a very strong template feature in which you can assign a particular posting to a particular template and when it is to display that particular post it invokes a specific PHP program to do the display any way it wants to. I came to realize how really powerful Wordpress is, and if I had known it three years ago I might have chosen it over what my blog uses, B2Evolution.