There is also a interesting theory on The Speaker, one I believe and if true would have just turned the story more interesting. Do not read if you have not gotten to and beat the first mission on Venus, better if you have also already beat the story.
That is an interesting theory, I like that. With the various factions vying for power in the city, something like that could set up for some sort of civil war (possibly using the Crucible as a proxy) amongst the Guardians.
Also (although I'm sure others have noticed this), it seems the second expansion House of Wolves will be about the Queen since she took over that Fallen House by killing their Kell. Maybe they'll turn on her and we'll have to clean up the mess, or something. Certainly I want to know more about the Awoken in the Reef and hopefully learn more about the Fallen society (such as it is).
As for areas which seem like they're ripe for being opened up, on Earth the area around Skywatch (I think) where the Hive and Fallen are fighting each other (not the trainyards, it's a later area story-wise), there's an opening where the Hive are exiting. I went in there and cleared it out. You can't go far, but when you reach an area where the way forward is all collapsed, a new area name popped up, something complex. Perhaps that'll be something we'll eventually find a way into.
I'm hoping the expansions are going to truly be that, not just a new set of story missions, but areas opened up in old locations. I know there are mentions of new maps, gear, etc, but I figure the maps are pvp, so I hope there will also be more areas opened in pve. Still need more details before I'm willing to get them though, £35 is a bit steep to pay on trust.
And finally (didn't expect to ramble this much) my Warlock got her first legendary... for a Titan. Well, in the vault it goes, my Titan will get from level 4 to 20 one day.