So, in TBC it's looking like the MH sword upgrade goes Spiteblade -> Talon of Azshara -> Blade of Infamy and the OH goes... Latro's/Revenger -> Quickening Blade of the Prince (which is MT and not released yet) -> Blade of Savagery
So it pretty much looks to me like you won't get an OH upgrade between Kara and Black Temple, without blacksmithing or PvP.
I'd say PvP is a solid option, considering the high ilvl (and thus DPS) of the weapons. Back at T4 people who didn't want to bother farming Latro's simply went for the Glad quickblade. My advice is to just do the same and go for the Merc Glad until T6.
For the MH it goes like this: Talon of Azshara > S2 MH > Dragonstrike > Rod of the Sun King > Talon of the Phoenix > S1 MH > Dragonmaw ~= Hope Ender > Spiteblade > Drakefist Hammer, with the appropriate spec of course (that means 15/46 for Maces or Fists).
For the OH it's: Blade of Savagery > Quickening Blade of the Prince > S2 OH > Latro's ~= S1 OH > Blazefury > Blazeguard > Fireguard > Revenger.
Dragonmaw is slightly better than Hope Ender but the DPS difference is really small, same with Latro's and S1 OH.