The last book fell into the codex category of having a good amount of interesting units and rules to play. But no one cared because we play this game to win! So most people only really see one or two kinds of lists because those are the only ones that work. Vehicles in 5th where the Tyranids problem.... unless you spammed hive guard and tricked your opponent into coming close.
Oddly enough with the change to 6th I've seem a lot less vehicles. If it wasn't because of the change to gun-line lists that might have actually breathed life into the 5th edition codex, but there are just too many guns right now for slow hoards to work unless you've got some tricks up your sleeve. Another thing about 6th worth mentioning (even though I hate that it left) is the removal of fearless wounds, I've seen this to be a big boast for Bugs.
Now with the next book coming out I'm curious how the Bugs are going to evolve into 6th. Here is a few things that I'm hoping hit the tables.
We need a army that makes this happen. Daemons was a nice try, but I largely feel that book was an attempt to create a jack of all trades with the whole 4 god thing going on...... and then somehow they all got lost in pulling it all together into the final product.
A lot of the issues Tyranids have had with vehicles have kind of evaporated. They're easier to hit, you can glance them to death, and they aren't pill boxes that hide assault troops anymore.
So I hope they push the book more towards eating things rather than creating some hybrid shooting/assault book.
2. Board control:
Tyranids need to be able to get everywhere. Your over there, well they need to be there two. I'm guessing they'll remove assaulting out of reserve for ymgrls but bugs should keep the random unit outflank, infiltrate, or appear out of nowhere rules.
And they need to have massive swarm or tough as nail units that can stay there.
Tyranids have always had a lot of units, but they have really failed at making them all usable or having a balanced FOC.
If they are really dead set on Allies and Tyranids not having them, their codex really needs to have all their units be usable. Being so isolated means they really need to have good internal and external balance against the the other armies, because unlike the other books they aren't going to have the option to add new things to their roster with new releases.
This could be wrong with the advent of supplements, but they have been really hit or miss so far. And I don't like the idea of supplements being used as band-aides.