My Opinion
Same design as the iPhone 4? 10% chance, it's most likely that Apple want a new design after the iPhone 4's antenna fiasco!
New design? 90% chance, although i think it is likely that the iPhone 5 will have a new design, I don't think it will be a drastic redesign, more of a subtle design change with a new antenna.
iPhone 4 becomes the low cost model? 90% chance, it is very likely that this will happen as it always has in the past, although some parts, eg the glass, may be changed to reduce cost.
No home button? 0% chance, I just don't see it going, changing to something larger/smaller maybe, but not going all together.
Larger screen? 60% chance, I thought it was more of a 50% chance before, but the recent case leaks make me think it may be happening.
Better resolution? 0% chance, if the screen is 3.5", the res will stay the same, if the screen is enlarged, I think the res will drop slightly, but still be more than 300PPI.
White model? 100% chance, especially after waiting so long with the iPhone 4.
Better camera? 100% chance, the camera has always been upgraded and i think it is nowhere near as good as it could be.
1080p recording? 50% chance, it depends on whether the camera is upgraded enough for it.
Curved screen? 0% chance, I just don't see it happening!
NFC? 25% chance, its possible, but I just don't think it's mainstream enough for Apple to justify wasting battery life with it just yet.
Enhanced voice control? 10% chance, I think it has to become more refined and reliable before it can be enhanced.
A5, more RAM and better battery? 100% chance, I think these are the three things that we can be certain of.
64gb? 75% chance, I think now SSD storage is getting cheaper, there will be a 64gb option this time round.
HDMI output? 0% chance, the iPhone has airplay for that.
4G? 25% chance, like NFC, i dont think it's mainstream enough for Apple to warrant the battery life for.
And finally, at this point and after such a long wait, I think the event and thus the release of the iPhone 5 could be announced any day now, I think Apple are trying to hurry as best they can though as I'm sure they'll know that contracts are ending and customers are jumping ship.
They're my thoughts anyway.