Assuming they have the same aspect ratio as the current iPhone (9:16):
4.7" iPhone at 441PPI: 1806 x 1016
5.5" iPhone at 441PPI: 2114 x 1189
Those are some weird-ass resolutions, which makes me really doubt this report (more than I did before).
1028 x _768 - iPad non-Retina
2048 x 1536 - Retina iPad
_480 x _320 - iPhone 1/3G/3SG
_960 x _640 - iPhone 4/4S
1136 x _640 - iPhone 5/c/s
2272 x 1280 - iPhone 6 ???
For the 4.7" @ 2272 x 1280 it would be 555 ppi
For the 5.5" @ 2272 x 1280 it would be 474 ppi
I would assume Apple would just double the resolution again.
That seems to be their tendency more than anything else