RAW Power 3.0 will be a front-end for the Photos library, but there are a lot of limitations imposed by Apple. For example:
1) There is no ability to read or write keywords, or any metadata except “favorites” and creation date
2) Aperture adjustment data is not readable, because it will have been converted before RAW Power could read it.
I plan to add ratings and flags to the Photos library, though it’s crazy what I have to do to get it to work.
Some restrictions may be relaxed in the future (like keywords). I am pretty sure the adjustment data is a lost cause once it is in Photos, though.
The feature set for RAW Power 3 is continuing to fluctuate, but I will share it once I feel that it’s stable enough to not disappoint people if I have to pull something important to get a stable release out to people.
I have not considered the idea of migrating LR data to RAW Power (or to Photos, then readable by RAW Power), but it is conceivable. As usual, the problem with moving data from LR or Aperture to RAW Power is that RAW Power (or Photos) is simply not as mature a product as either LR or Aperture. RAW Power cannot represent all of the data that those apps store. I’ll have to think about it.