Tyranids are currently being playtested, which means that the rules and ideas being thrown out will change, be altered, dropped completely, and in most cases not look like they do now. Still we have not seen anything specific, and I would imagine that we will not for a while.
There are no specific playtest rules here, which is fine, because its more important at this stage to see the direction that the codex is headed rather than specific rules. (although specifics are always fun and exciting to see).
Please remember that these are ideas that are being tested currently, and that it is still early as we do not expect tyranids until next year sometime. However this set does answer some questions that we still have, like dedicated transports, FoC changes or not, and some very cool ideas like Evolving your bugs for specific battlefield roles.
via a source that must remain anonymous (for obvious reasons)
Tyranids are still being playtested.
Some royal court type stuff with warrior primes.
Point reduction on the little bugs.
Some interesting FoC rearranges.
Several new bugs (not all will make it).
The ability to tailor make your bugs and "evolve them" into being very specific, or keep them cheap and generalized.
Better ways to help close with the enemy.
Feels very "overwhelming" to play against them.
No new transport options, but a couple new deployment options.