The slim was released at the end of August/Beginning of September this year. The model before that was the 80GB 2USB slots, no Backwards Compatibility, in summer of 2008.

The answer to your last question in your last post, as well as your original question, is no, you probably shouldn't buy a unit with more storage, nor wait for a bigger storage unit. If you need more hard drive space, you should buy it yourself, since replacing them on PS3's is super easy - you litterally unscrew something, slide out the drive, then slide in a new one and screw it back on. Getting your own hard drive is super cheap compared to the $50 you'll spend extra on a 250GB.

There's many solutions instead of getting a hard drive as well. Like people have said, if you ONLY use your PS3 to play video games, than your game installs will probably never fill it up. This is mostly true because fewer and fewer games on the PS3 are running on installs anymore. Because Blu Rays are so massive, they just run the uncompressed data. Also, I usually expect a demo to be larger than 1GB, but they too are beginning to get smaller, plus you can always delete those once you know you're done with them. Same for video files.

However, if you want to use your PS3 to watch downloaded videos and movies on your TV (like I do) and save some of your music collection to play with games that have custom soundtrack enabled, or hell, even put your photos on it to look at them through the cool photo viewer, then this is where other solutions come in. External hard drives are even ridiculously cheaper than internal ones, so you can just keep that plugged in via USB to your PS3 to accomplish that. Of course, you can choose not to buy any hard drive at all. You could just download a media server application. If you have wireless or can broadcast a signal, your PS3 will be able to pick up media servers and stream them wirelessly from your PC. If you have a decent connection, this is probably the best and easiest way to go.

Recap/For those with attention deficiency disorders, here is a summarized snippet of the general ramblings for you to ponder over -

No, you shouldn't buy a more expensive model/wait for one with more storage. You should buy the cheapest one, and if you find you need more space, either a) buy a hard drive on your own, b) buy an external hard drive, or c) download a media server application.

Any of these solutions would be much cheaper and much better than spending the extra money.