I think there should be some way they could easily add code to enable different screen resolutions even if it is only 2 different resolutions(current, and higher resolution) like apple does with the iphone and ipad.
Well.... there is an issue with that. The iPhone has two resolutions, yes, but can scale perfectly. Why? Old iPhone res: 480x320. New iPhone res: 960x640. Perfectly scaled. Each "old pixel" can map to an exact 2x2 square of "new pixels," and the OS can even apply a high resolution font render into all applications reguardless of display support, too.
iPad, has not had this issue.... yet.
However, no company is expanding on 800x480, so far. Unless if we see an odd 1600x960 (or something with an identical display aspect ratio) developed, we will not see a continuation of the old ratio (there is ONE other way... a 16:9 display with softkeys, just like the Galaxy Nexus, but specifically sized to allow for ~16:9.5 ratio to match old display ratio). Those are the only ways to see perfect scaling for older applications (and even so, the second and third option would give subpixel rendering issues as many GUI elements, in say, games, are bitmap, and not vectorized; only one is likely, as the other two would possiblely be utterly ignored on phones, as 1280x720 does hit the 300PPI "retina" limit quite well, even at massive screen sizes (for a phone).
However, it's just an interesting issue, and I am curious how MS will tackle it. Android, since it was always open on this from day one, has had a DPI (PPI, technically) scaling setting, and many applications can easily scale from tablet to phone size without any special coding. Though this does introduce another issue of PPI filtering in the marketplace.