Judging from the last interview, they mentionned an intended first increase up to level 60, so I guess it will be 10 levels each time. However, I don't recall anything about "each patch release".
My guess would be level 60 at 5.1 and level 70 at 5.3...which could still open some very slightly chance of having lvl80 at 5.5, unless they indeed give us a new limited job during 5.5.
