You can still change instances by clicking the instance name at the top of the minimap (or in the main map) but it just no longer prompts you when you zone from one to another. I guess if you where trying to meet someone in a specific instance # that would be useful.
I guess this was indeed just a beta thing. Instance hopping could almost be a cheat to zone into a defend sector mission and find one that was started to avoid waiting for 5 minutes or even one half done. If you wanna meet up with a friend then form a team. If the feature is still there but hidden then great but I can see why they might want to remove this visibly, transition from one instance to another should be seamless. How many other MMO's out there have you seen where you can choose which instance number you can zone into?