According to the LAX twitter account, US is moving to the four new T-6 gates on November 6 and leaving T-3. Makes sense given that AA had to relinquish 2 of the 3 T-3 gates held by US after it moved from T-1. US has still been using them on a common-use basis.
https://twitter.com/flyLAXairport/status/527484707341340672
The tunnels connecting T-4 to T-5 and beyond re-opened the other day for the first time in 13 years, so you can walk between all gates on the south side without re-clearing security. Also, LAX (and other airports, I believe) now permit you to enter any terminal and clear security there as long as you have a valid boarding pass for any terminal at the airport.
https://twitter.com/flyLAXairport/status/527484707341340672
The tunnels connecting T-4 to T-5 and beyond re-opened the other day for the first time in 13 years, so you can walk between all gates on the south side without re-clearing security. Also, LAX (and other airports, I believe) now permit you to enter any terminal and clear security there as long as you have a valid boarding pass for any terminal at the airport.