That's a v2 feature.

Is there a rough v1/v2 timeline? The thing they wanted to release by the end of the year is v1 I assume?

Is v2 just a software update? Does it require sending a whole new set of satellite or it something they are planning to patch into existing satellites someday and have inter-sat support?

The original plan required a laser link, but those were removed from the v1 satellite because the lasers would survive reentry and SpaceX didn't want their satellites falling on anybody's head. So this is definitely a hardware upgrade requiring new satellites.

But that's not a big stumbling block -- SpaceX plans on replacing 1/5th of their constellation every year.