Apple has been a pretty consistent company. Just look at their releases:
iPhone 3G: 412 MHz Processor, 256 MB Ram, 3.5" 320 X 480 with 165 ppi Screen
iPhone 3GS: 600 MHz Processor, 256 MB Ram, 3.5" 320 X 480 with 165 ppi Screen
iPhone 4: 1 GHz Processor, 512 MB Ram(2x), 3.5" 640 X 960(2x) with 326 ppi(~2x)
iPhone 4S:1 GHz Dual Core, 512 MB Ram(2x), 3.5"640 X 960(2x) with 326 ppi(~2x)
iPad 2 : 512 MB Ram, 1024 X 768 Screen with 132 ppi
New iPad(3): 1 GB Ram(2x), 2048 X 1536(2x) with 264 ppi(2x)
So we see that after every two years, the device gets significant bump in Resolution and processing power. Now we already know that the new iPhone is going to have A5X Quad-Core, which is in the New iPad, but about the screen resolution we have the perfect idea:
iPhone 5: A5X Quad Core Chip, 1 GB Ram(2x), (~4"?)1280 X 1920(2x) with 326+ ppi
iPhone 3G: 412 MHz Processor, 256 MB Ram, 3.5" 320 X 480 with 165 ppi Screen
iPhone 3GS: 600 MHz Processor, 256 MB Ram, 3.5" 320 X 480 with 165 ppi Screen
iPhone 4: 1 GHz Processor, 512 MB Ram(2x), 3.5" 640 X 960(2x) with 326 ppi(~2x)
iPhone 4S:1 GHz Dual Core, 512 MB Ram(2x), 3.5"640 X 960(2x) with 326 ppi(~2x)
iPad 2 : 512 MB Ram, 1024 X 768 Screen with 132 ppi
New iPad(3): 1 GB Ram(2x), 2048 X 1536(2x) with 264 ppi(2x)
So we see that after every two years, the device gets significant bump in Resolution and processing power. Now we already know that the new iPhone is going to have A5X Quad-Core, which is in the New iPad, but about the screen resolution we have the perfect idea:
iPhone 5: A5X Quad Core Chip, 1 GB Ram(2x), (~4"?)1280 X 1920(2x) with 326+ ppi