Version Two of "Four Arm Race Idea"
Its been awhile since a good update to this thread, and I'm currently not satisfied. A few suggestions to make things simpler and smoother.
First off, anyone can wield a versatile weapon in one hand, I assume you want them to gain the +1 damage bonus as well? This is going to look really messy with your version of the race however, since the rules are different for small creatures with versatile weapons. I would strongly suggest medium (which I believe the Thri-kreen are in many supplements).
Excellent, Excellent.

My only quibble is that I don't believe that a "small" four armed race is more complicated than what you propose except that a small creature would not be able to use 2H weapons (including your double weapon) according to my understanding of the rules.
I used your previous advice to create my race the "Formici". Your ideas for Thri-Kreen birth castes are very similar to my own.
FORMICI
The formici are a race of sentient insects that live in massive earthen towers containing hundreds of creatures living in a communal society. Only a few of the race are fertile. Male drones and a single female queen. The rest are infertile. Most are happy working for the common good of their hive, but the few defiant, unscrupulous, or adventurous enough to live among other races are known as the "Unhived".
Birth Caste:
Birth caste is extremely important among the formici. Not only is a young pupa trained from birth to perform a specific task, it is also genetically evolved for it.
Queen: The queen is a massive russet scaled creature that gives birth to all the citizens of her hive. She is the mother and ruler of her community. NPC Mature queens are barely mobile and both politically and socially anchored to their hive. Immature queens are thin, spritely, and royal red. Young queens are encouraged to leave and establish new hives and open new frontiers. Some young queens are accompanied by a small court (a few of each caste) to help create a new hive. Others are send out alone without any assistance from the parent hive. Attribute Modifiers: +2 INT or CHA. Young Queens always take "leader" classes.
Soldiers: These insectoids have heavy purple exoskeletons providing durability and increased strength. They are obligated to defend the hive from threats foreign and domestic. They are the first line of defense, guard the queen, and lead the hive in war. Attribute Modifiers: +2 STR or WIS. Soldiers are genetically tailored to "defender" classes.
Scouts: These yellow-green insectioids find new resources for the hive or engage in trade with other races for their hive. Scouts are expected to be resourceful and creative. Attribute Modifiers: +2 WIS or CHA. Scouts embrace "striker" classes.
Overseers/Commissioners: These blue insects are trained in religion, natural science, arcana, and civics. They plan the development of the hive both physically and spiritually. Attribute Modifiers: +2 INT or WIS. Commissioners are genetically predisposed towards "controller" classes.
Workers/Proletariats: The largest group, the grey proletariat carry out the grand plans of the commissioners, form the hive militia, and carry out all the domestic labor of the hive. Some are trained in specific crafts to provide trade goods for wealthier hives. The worker proletariat is accustomed to heavy manual labor, deprivation, and harsh living conditions. They have only a remedial education centered on duty to the colony and hive folk-lore. Attribute Modifiers: +2 CON or WIS. A worker proletariat would never become an adventurer, but an Unhive worker pursues "primal" classes exclusively.
FORMICI Racial Features
Attribute Modifiers: +2 DEX plus the birth caste modifier (See Above)
Language: Deep Speech and Common
Racial Skill Bonuses: +2 Dungeoneering, +2 Athletics
Vision: Low Light Vision
Speed: 6
Size: Small
Racial Traits
Four Arms:
You have a set of lower arms that have all the agility and strength of the upper set allowing you the ability to hold up to four hands worth of equipment. You may use any two hands worth of weapons/implements each turn (except with the "Four Arm Flury" racial feat). If you use an attack power with a 2-handed weapon or with two weapons, you can not employ a hand held shield until the beginning of your next turn (you do not drop your shield(s), you simply no longer act as though you have them equipped). If a power requires you to be wielding two weapons or a shield, you cannot use a 2-handed weapon as part of that power. This racial trait
does not allow you to equip an additional arm slot or ring magic item.
Multi-Dexterous:
You can draw or stow an item as a free action. You are limited to 1 item per turn.
Racial Encounter Power
Four Arm Flurry
Encounter Minor Action Melee or Ranged: Weapon or Implement
Requirement: The Four Arm Flurry must follow up a successful attack.
Benefit: Make a basic melee or ranged attack with a hand held weapon or implement you have not yet used during this turn as a minor action.