Secondary Carrier Component will always be released during handover procedure.
There can be multiple scenarios where Scell(Secondary carrier component) may be added,released or modified during handover.
1 > Scell is already configured in source Pcell(Primary carrier Component) and Scell is not modified/released at target Pcell.
2 > Scell1 is configured as a part of source Pcell which will be released after handover to target Pcell and can be configured with Scell2 in target Pcell.
3 > There can be possibility where UE can be configured with Scell in target Pcell.
4 > UE can also be handed over to Secondary carrier component where UE will be given with mobility control info with Scell release and PCI and target EARFCN of Scell.
5 > UE can also be handed over to Secondary carrier Component where UE will be given with mobility control info with Scell release and Scell configuration as that of Source Pcell which can act as Scell if UE is handed over to the Scell(i.e. Exchange of Pcell and Scell).