How do you know?

As I have said, Blizzard has stated that they intend to change how tanks feel in pvp. They are no longer intended to be extremely hard to kill.
And Healers are capable of killing people even today. They lack burst, but they have strong DPS in pvp.

In terms of duels for example: They will win, just because they can wear everyone down.


Anyway, I think it is way too early to jump to conlusion here. Balance has not even remotely started now, they are still determining the way how a spec should be played and what they should be capable of.
Though I wouldn't expect any big difference from now how the overall meta game between ds, tanks and healers will be.

What I can see is that maybe in arenas there could be room for a healer tank dps team ... but this is only an option if healers aren't that powerful anymore.
If you need 2 dps to be able to kill a healer or healed target, then you can't bring a tank unless either the tank can fully dps or the healer is not as strong in pvp anymore.