I'm watching the Infusion part of the stream again and from what I gathered it seems like you can get any year 2 legendary or exotic up to the max light level as long as you infuse it with a stronger raid level weapon, so thankfully it seems we won't be going back to all looking the same like we did pre-HoW.
This brings up again question though, because if old legendaries don't break down in the new materials and they can't be used for infusion since they have a lower light level than even the green weapons, then what the fuck is the point in keeping them? The only reason I can see for keeping them is the gear check Bungie are meant to do on launch day.
On the vault space thing, I'm someone who has never had problems with vault space the expansion announcement didn't do anything for me, all I saw was more empty blocks that I'm never going to use, so the stream would have been far better for me if they had just gotten done with the vault space thing at the start and focused on the more important stuff for the rest of the stream, instead of the cringe worthy and staged build up that we got.
Alas, it is the number most asked for feature from the community, so Bungie had to make a show of it I suppose, but with our old shit being made obsolete, is vault space even an issue anymore, or are people still going to be hoarding shit they don't use? Who am I kidding, of course hoarders are gonna hoard.