If you get a newer 40gb, 80gb, or 160gb console, you will have to wait for Sony to implement backwards compatability in a firmware update.
Firmware is like an operating system and Sony updates, improves and adds new features every 3 months or so.
The best thing to do is buy from a retailer, just in case Sony ask for proof of purchase, because you will need a material copy in the event of a warranty repair. Also, buying from a retailer gives you a warranty period with them also so if anything went wrong with your PS3 you could take it back to the store.
PS3 games slus are regional, but the games themselves are not region locked, so you play an NTSC game on your PAL ps3, or NTSC-J on your NTSC etc.
Unless the PS3 has 4 usb ports, 20gb, 60gb, or the early 80gb model then it isn't backwards compatible. If you really need backwards compatability to play PS2 games you can buy one 2nd hand or new from eBay (most retailers won't have them in stock anymore).