licensing - SAP Info Steward and DQM

I have to make a choice between a standalone licence for Data Integrator vs full fledged license for Data Services (including IS and DQM components).

I wonder if I go with Data Integrator, will I have option of separately licensing (option to upgrade) DQM and IS later on?

Or whether I will need to buy full Data Services license in future.

This is simply a question of license flexibility.

Thanks for your inputs.