Hmmm... Under SAS Viya the front-end to build ETL processes will be SAS Studio. In the latest version for Viya there are already some transformations for ETL available and there are more to come.
At one point in the hopefully no more too far future there should be a migration path from SAS9.4 based DI Studio jobs to SAS Viya based SAS Studio jobs.
Right now we're in this transition phase and I'm not sure how many new projects there will be still using SAS DI Studio for a new implementation. I would expect that SAS DI Studio will still be around for quite a few years and that there will be BAU work and also more and more migration work from DI Studio to Viya SAS Studio jobs.
If DM is your home-turf then I'd probably focus to understand how metadata driven DI Studio works in principal and what transformation it has. And then I'd focus strongly to understand what's already available in SAS Studio under Viya and I'd stay on top of any new Viya releases and what they add to DM capabilities.
As for getting into DI Studio: It's unfortunately not part of any free-of-charge learning/academic edition so you would need to work at a site that has it licensed. I'm also not aware of any free e-learning for DI Studio. The documentation is free and there are white papers. If you've got already experience with another metadata driven ETL tool then that might already give you a good idea how things work - else not sure how far the free information can get you.