One of the featured planned for the next major content patch (3.3) is the ability to form groups across multiple realms. It's unclear at this point whether it will be through the LFG tool and if it will be limited to realms in your battlegroup, but it's a definite improvement. Additionally, the friends tool is being overhauled to include all battle.net accounts, allowing chat between any accounts, regardless of which server they're on or which game they're playing.

Also, the next expansion is going to update Eastern Kingdoms and Kalimdor so as to allow flying mounts.

From what I've heard, they didn't all get to 80, the raid had a lot of 70/71s. The best level 70 gear (which they have plenty of) is still better than most of the pre-raid gear at 80, so they were already well geared for this. And as you level, your gear actually gets weaker due to how combat ratings work.

Furthermore, the bosses are considered to be 3 levels higher than players, be they 80 or 70 (or 1, for that matter). The main reason to level up is to actually use the gear that drops from these bosses (the gear requires level 80 to be equipped).