How to consolidate project areas into team areas?

There is no tool that will automate this. You will need to create the team areas, and then manually bring over the information (or write a program that uses the RTC API to automate it). Note that this cannot in general be fully automated because the metadata in the source project area (such as roles and work item types) may not be compatible with what is available in the target project area (I assume in your case, the process areas are compatible). If the project areas are in the same repository, then you can "move" the work items over.

Cheers,
Geoff

Have too many project areas which should be just team areas.

Is there any tool available to help consolidate project areas into team areas of one or two existing or new project area?

An scenario as below:
Project areas: A, B, C, D, E, F, G;
Target action:
Make B, C team areas under A;
Make E, F, G team areas under D;