Is it possible to max 2 skill trees?

Solution 1:

Yes, if you have the Ultimate Vault Hunter Upgrade Pack, which increases the level cap to 61. For example, see this Salvador/Gunzerker build which maxes out two skill trees at just level 57:

Solution 2:

I don't think (for now) you can.

You get 46 skill points at maximum level (50), and if you head over their character planner you see this:

• 1 skill point is "wasted" for your gunzerking ability

• fill out the first skill tree -> you will need at least 26 skill points

• this leaves 19 more points --> you will need 7 more points to have another tree filled completely

In early 2k13 level cap will rise. In the first Borderlands, after the expansion, you could. So maybe in this chapter it will be possible too

Solution 3:

You cannot max out two skill trees as of now. At max level (50) you have 46 skill points. You would need 7 more skill points to reach the last tier skill of another branch. At this time, it is unknown what the level cap will be raised to, but there is an intended level cap increase which could make this possible in the near future.

Note that skill bonuses from class mods do not count towards unlocking the next tier of a branch.

The borderlands 2 website has interactive skill trees if you want to plan out your build: http://www.borderlands2.com/us/skilltree/