Nope, don't believe this news at all. Even though April has already gone it still sound a bit fishy, to good to be true.

...and I have it under good authority from a very reliable source that Zelda will be a launch title on the ps3 and Mario will launch on the 360.

I don't think that this is so far off the mark. I can see M$ trying to steal customers from its competitors in this way. Sony, less likely and Nintendo, very unlikely.

If they did try to do this, they would face massive legal problems though, as the companies involved wouldn't take it lying down.

As M$, $ony & Ninty's next-gen machines will be Wireless-G enabled, I guess it's possible for multi-platform games to be cross-platform multi-player; via Ad-Hoc peer-to-peer.

Could the next-gen machines become Wireless Access Points, for the DS and PSP to connect to the internet?

My best idea of what this could indicate? A cross-platform messaging system, or the ability to link up the same game online between the different systems. The latter was suggested in this current generation but never succeeded due to the disparities between each consoles online network. Knowing that all next-gen systems will be online, it seems like a good idea to explore that possibility again.