I am helping prepare a team for First Lego League and the new EV3 kit is what will be used. We are currently teaching the kids with NXT 2.0 kits that we have using the NXT-G IDE. It appears that we cannot get the [free] EV3 Home Edition software until September 1, 2013, losing important time and requiring some learning curve. Is it possible for us to continue using NXT-G software to program the new EV3 kit when it arrives?
No, it appears that you need to use the EV3 software to program the EV3 kit, as per the FAQ on the LEGO site: http://mindstorms.lego.com/en-us/News/ReadMore/Default.aspx?id=476781
The EV3 sensors also won't work with the NXT brick either.
Though, I'd imagine if you're getting an EV3 kit, it should come with the EV3 software.
I think I found the answer from a post back in January (unless things have changed since then). It came from user named bungeshea, who said "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". So I assume the answer is NO (unless someone creates an NXT firmware upgrade that can emulate the EV3 API...highly unlikely).