Here is how i see the role of a retri paladin in wotlk pvp. I think his damage will be less devastating like now on ptr, comparing the health buffs what other classes get(150, 130 staminas on deadly glad. items).
With the "everlasting" mana pool, being in plate, and with the biggest HP buff(ret pallies now have around 11k hp in pvp gear, while in wotlk they will get the same amount hp as warriors and dk-s, 150 sta on deadlys) and with the support ability they have(freedom, prot, cleanse, heals-even instants), i think they will be the warlocks counterpart. Lock is an offensive outlasting char, while paladin will be a more defensive(sacred shield, bubble, utilities, stuns etc.), but also outlasting char (have lots of mana, hp, armor, protective spells).
And i like this way, because this is the role of a PALADIN, this was in w3 and also in every game.
Thats what i expect from Wotlk, it can happen that i was wrong, but i am eager to see my dreams come true