The PS4 is not backwards compatible with PS3 discs. Sony plans to allow you to STREAM PS3 titles from the Gaikai service to your PS4, kinda like how you can stream a game from the PS4/PS3 to your vita.
The downside is lower video quality, increased input lag from the controls and the requirement to have a sufficient internet connection. While its better than nothing, it certainly is not nearly as good as being able to play the game right from the console itself, be it disc or a PSN download. You can basically forget about competitive online play, or any game that requires quick reaction/timing.
I hope you are joking by thinking tablets will replace consoles. If anything, you should compare tablet gaming to other mobile devices, like smartphones, DS and Vita systems. If you think playing Facebook games on your tablet are going to be better than playing full high budget games on a dedicated console you are sorely mistaken.
LMAO tablet gaming. Hope you like bejeweled clones and shitty ports of games made for other systems (usually multiple years old). Releasing new versions of consoles to lower the manufacturing margins (and then the price) is really standard practice and has been for over a decade now, nothing really surprising here. Some people will buy them, some people won't.
Your kidding me? You don't know what "good" hardware is. I use a tablet (Kindle Fire HD) mainly for Minecraft on the go and some other android games. I like the Kindle because its android (open source), and you dont have to pay for anything. Lol, Aptoide has all your apps you need covered
Console is basically a PC. Installing Windows or something like that gives you the full PC power. The PS3 and PS4 have the hardware. just the OS needs to be able to support PC criteria.