Let's look at some math:
LBH paid 1.58 billion for roughly 26% of Archstone. That would value Archstone at just a hair over 6 billion. But
Archstone has 70,000 apartment units (as compared to ER's 150,000)which are largely upscale and thus probably produce a bit higher RoR than ER, so sold as a whole or taken public it may fetch in the 8 to 12 billion range. 12 at the very most.
I doubt that Archstone is LBH's end play, but rather just another step toward it.