I doubt 6 months... The Naxx farm is long and intense... I say TBC between September to November, giving Warmanes history with Frostmourne, I say each xpac will be 1 year not 6 months
From the Announcement of Onyxia's Launch, we know:
June 29th, Phase 5 will culminate with Naxxrammas.
That's 6 months from now. We'll probably get AT LEAST 2 months of Nax before TBC launches. That's 8 months. I doubt they'll open Nax and delay further progression so that Vanilla lasts a full year...we'll probably have a total of 9-10 months in Vanilla (including the last month since Onyxia launched) before TBC Launches.
From the Announcement of Onyxia's Launch, we know:
That's 6 months from now. We'll probably get AT LEAST 2 months of Nax before TBC launches. That's 8 months. I doubt they'll open Nax and delay further progression so that Vanilla lasts a full year...we'll probably have a total of 9-10 months in Vanilla (including the last month since Onyxia launched) before TBC Launches.
That's just my speculation though.
Ye it's a logical assumption. Doubt they'll give naxx less than 2 months to run, it just won't make any sense.