Skill points due to intelligence increase.

[Mathias]

The headbands handle languages by adding extra slots because languages have to be added by bootstrapping them (skills are handled by modifying a skill that's already present). Setting up language bootstraps could only be handled by A) making a headband with the language(s) already fixed (P.S. If you're giving out a specific headband as treasure, you may want to make that custom headband in the editor for your players), or B) Offering a table on the magic items list that would let you select the language, and then somehow tie the languages to the specific headband that offered it (for example, what happens if you own one headband +2: Elven and another headband +2: Dwarven).

So, there's no good way of handling languages granted by something other than a race or one of the general language slots on the personal tab. So I just went with the simple method and added the slots.

[Leonal]

Hmm, what I meant to say was that I can't find anywhere that says you get any additional languages by wearing a headband, since languages granted by int bonus are only given at first level.
I don't think you don't get a new language by raising your int through leveling or any other means.

[Vrischika111]

it seems that permanent ability increase gives backwards benefits (which was not the case in 3.5).
While JJ does not explicitely mention "language" he says all "other benefits"
http://www.d20pfsrd.com/basics-abili...elligence-Int-

[Arkamit]

The bonus languages are specifically called out to only happen at the start of the game not per later increases.
While it is true that James Jacobs, while he is clarifying about skill ranks – supporting the text as written in the rulebook and by paizos own writers, choice of saying that “All bonuses are retroactive” might be interpreted quite liberally I would not without further errata/corrections use this to supersede what is written in the rulebook and published adventures.
If they meant to say that what they themselves have written in the rulebook, on page for headband of vast intelligence and in many adventure paths are incorrect - it would stand to reason that they would include it in the errata.

Otherwise I would cautioun to interpret a clarification (which is what he is trying to do about why/how of skill ranks per level) as a correction of the rulebook (which is what it would be if later int bonuses effected languages). His choice of “All bonuses are retroactive” might just as easily be interpreted somewhat more moderately to the clarification that “all per level benefits are retroactively effected”, which would fit perfectly with paizos own published material, instead of the correction that “STARTING bonuses” are retroactively affected - which is obviously not something paizo themselves are doing.
What paizo was aiming for was that per level boni should give "backwards benefit" - it has yet to be stated that they want to change STARTING stats.

While I am not disputing that it might be a good change, and that we might see an errata/word of god comment to this effect at a later date – as per the current rules this is not the case. Just check any published adventure or rulebook and find that while Headbands of Vast Intelligence grant X number of extra skills, that are listed in paizos own materials, it is never mentioned that they grant any languages.