Windows 8 / Phone 8 Apps Universal?

Anyone know if apps will be able to be universal (like iPhone>iPad)? This is one of my biggest concerns... iPhone and iPad set the bar with the fact that all iPhone apps work on iPad and some even offer universal apps. Plus the fact that iOS is being pushed into OSX I wouldn't doubt they will work across all Mac computers sooner or later. Unfortunately with W8/WP8/Xbox8, or whatever they end up calling it, I am not sure if I am buying into a single app ecosystem. If Microsoft ends up selling a Surface phone down the road without this I see it as Microsoft shooting itself in the foot. Hell the fact that Windows 8 and WP8 look so similar thanks to live tiles, both offer apps from a Store tile, and all the talk of bringing Windows to WP8 if apps don't work similar to iPhone to iPad they may have already shot themselves in the foot.