The EV3 is coming in Fall/Summer of 2013 and we tons of unknowns that will come in EV3. I am curious what software EV3 will run and will older generation software run on EV3 (NXT 1.0). And my final Question EV3 will work with Apple and Android devices, so that would mean iOS and Android developers could make application for EV3 or will only Lego make apps for EV3.
As you say, there are still tons of unknown at this point, so asking the question is way premature.
However, considering the software is said to be based on the same technology as the one in the NXT, it's likely it won't be too different, and that's why that software will be able to control NXT bricks. However, I also doubt you'll be able to control EV3 bricks with NXT software.
That software is going to work on Mac OS and Windows; it's likely the apps for Android will not be a full-blown development environment (although, it's just a guess, it would be way cool if it was).
As for third-parties, LEGO has been very very open about its software in the past, and they will be this time too - opening the door for a plethora of applications/firmwares/whatever on several platforms.
The graphical software that ships with the EV3 set can program both EV3 bricks and older generation bricks. We assume that this means NXT 1.0 and 2.0 bricks. However, it is unlikely that NXT-G will work with EV3 bricks as EV3 bricks run a custom build of Linux, whereas older bricks run a custom firmware.
LEGO will create an offical app for both Apple and Android devices, but other app developers will be able to use the API to interface with the EV3. There will most likely be some documentation available (as it was for the NXT), and perhaps a SDK available for download.