Basically not how this was intended for.
You'll have the option to have a partner account which you can create various sites within your portal where each site will be under its own plan.
Or you'll have an existing account which is designed for one site. So I would say ideally no but you could add multiple domains to a site account under one plan, but then you'll need to share the same account (meaning one shop, one set of system messages, layout, etc).
Those are the options at this stage.
Hope this helps!