I mentioned this in a similar post about the compo a month or two ago. I co-run the competition with Craig so here is my response
There are currently no immediate plans for a GBAX 2008, traditionally its held around this time but last year we left it until later (finished July I think) as neither Craig or myself didn't have much time. Pandora was part of the reason why Craig was busy back then
I honestly have no idea if/when there will be a GBAX 2008. If it was to happen I would guess it would be much later in the year to allow things to settle down with the Pandora launch (both the scene and for Craig), give time for developers to get used to coding on the Pandora and also time to write their software. I haven't actually spoke to Craig privately in over a month (turn your ICQ on Craig!) but I know he is very very busy so it is probably the last thing on his mind.
Also the problem is fitting it around other coding competitions, there are always others going on and we try to fit them around others such as the PDRoms and Neoflash ones who I have ties with. So working out a date at the moment is very hard
As for what platforms are supported, its basically down to what Craig and myself have. I think I mentioned in my other post that iPhone was not possible as I personally have no intention of buying one, the Gizmondo doesn't stand a chance as its a shit system and will likely flop in a month or two like last time (so we wont be buying one). The JXD or variant is a possibility depending on if there is enough interest and homebrew is running well. The list of support platforms will probably be GP32, GP2X, DS/GBA, PSP and Pandora.
Hope that clears things up.