I was expecting them to up the price for 1 month by say 10% and 3 months by 5% and then keep 6 months the same. This would make the 6 months look more attractive than it already is, and net them a profit on the lower pay tiers. This would incentivise more people to pay for 6 months upfront especially if they kept including mounts, pets, mogs or whatever.
They could even up the price of the 6 month also but have "sales" every 6 months or so that will return it to the current price. This would urge even more people to take that 6 month deal while its cheaper and on offer. None of this ofc is good for customers but would make them a fair chunk of cash and keep peeps subbed during periods of no/bad content.