First answer: The PS4 has not been released or even announced as expecting to be released
Second answer: I don't think they have even started to think about a PS4 as there still sucking in all the money they can from the PS3. (But I could be wrong)
Third Answer: It looks like it will be released in late 2012, check out this link.
http://www.ps4playstation4.com/ps4-release-date-countdown-begins
The countdown is under the main image.
No you will not be able to play the games either way. Systems changes on the PS4 allow them more design capability for games and many titles will be released in a downgraded PS3 version. You still will have to have a PS4 to play PS4 games and a PS3 to play PS3 games.
No
In short, no. Sony haven't released any information regarding a PS4 yet, so we can only assume that you cannot. It is highly likely you will be able to play PS3 games on it, that is - if it really comes out.
No, the PS4 does not have backward capability and cannot activate (play) PS3 or PS2 games.
No it will not
You will be able to play it on both the PS3 and PS4 gaming consoles. The beauty of Playstation is that you can access their games and titles via consoles, along with wireless and remote devices.
No, the PS4 will only run the games made for the system. But there is a application on PS4 called PlayStation Now which will allow you to play PS3/PS2 games for a price.
yes!
The PS3 will not be able to play the PS4. They both are on the Playstation Network (PSN) and Playstation Plus will work for both of them as it does for the PS Vita and PS3
No and neither console plays the others games
No the PS4 when it comes out will not play PS2 or PS3 games because it has proven to be a unlimited expense filled with great difficulties and problems if not an impossible task
Unfortunately the new PS4 will not be able to play any games that were available on the previous PS2 or PS3 consoles. However, Sony has stated that they hope to be able to offer this ability sometime in the near future.