I would love it!
Sometimes there can be too much black space between the tiles, and also some tiles have the need to show more info. And the large bing weather tile you see here, would look awesome.
Windows 8.1 has it, so small - medium - wide - large, so I don't see why they wouldn't do the same with WP8.1. At least now, after the update, when you make an app for WP8.1 it can work with W8.1. I guess that includes tiles too