I have the same question, having made a substantial investment in Garritan Libraries.

found this online:

https://forums.steinberg.net/t/simple-instructions-to-use-aria-player/673827/3

I would assume that it would work as VST is closer to an industry standard. I al still debating on making the jump to dorico.

Yes, ARIA Player works in Dorico.

The link above is for a very early version of Dorico, and most of the procedure is unnecessary.

You will need Expression Maps (which translate notation effects like dynamics, pizz, etc into the required MIDI commands). I have created a set for GPO5, along with Playback Templates (which setup which sample goes with which staff instrument; which ex map gets used, etc, etc). 

There's also percussion maps, and even an "Advanced ARIA Manual" for getting into the deep dark secrets of SFZ files and ARIA's internals. 

This is all slightly hampered by the fact that the Mac and PC version of ARIA are slightly different versions, so the PC version complains if you load something made on a Mac, as being too new for it. 

https://forums.steinberg.net/t/dorico-expression-maps-for-gpo5/158064/