If you squint at the perk chart in the Fallout 4 tease image, the perks seem to be grouped in such a way as to indicate 40 levels.
You start at level 1, and going across the top first, the first perks to unlock are the SPECIAL perks, where you can put a point into Strength (Lvl 2), and then Perception & Endurance (Lvl 3), and so on, leading to 40 levels, as there are lines around groups where two or three perks might become available at certain levels.
There are 7 perks per row, except the last 2, which seem to have 8 per row for the last 2, if you look closely. However, even if it is 7 per last two, the number of 40 levels as divided by those "downpipe" lines still stands.
Anyway, this leads to 40 levels. This assumes that every level unlocks a group of perk (at least 1), not every 2 levels.