Riot, how are the support items and their replacements going to work on treeline?

On TT, all still exist.

Twin Shadows is coming back in 8.4, and Shurelyas is coming back in 8.5.

Will only one of them be available on TT? Both? Will the actives be unique, or do we have to deal with Cho'gath running with both Talisman and Shurelyas?