I know its too soon, since we have only seen the SY cards so far, but i predict SY will be dominant, or shall i say, keep being dominant.
Why?
1. Its already the faction with the strongest deck, due to the buffs of the latest patch, and unlikely those cards will get nerfed on the 8th June.
2. Its support to a hypercontrol archetype, and control is usually favoured and more competitive than "pacifist" strategies.
3. Even though we havent seen the other new cards, we can see the theme they will have on the expansion page. NG will go some form of deck manipulation, NR will go some weird stuff with orders/charges, ST will go spells, MO will have some crone/organic theme, SK will go rain/weather.
Most of these wont be control, SK will be but rain/weather isnt as hard to play around as bounty. Maybe only ST will be able to face SY, if the spell stuff is unitless.