Damn I've barely figured out how to beat my friends Tyranids before, now I gotta deal with new stuff that usually will be much better.
Well in general, I'm thinking a lot more use of Noise Marines, Chosen outflanking in Rhinos with Meltas and/or Flamers, Rhinos with Havoc Launchers, and Lesser Daemons. Beyond that the usual DP (I actually dont use Lash as much, but still a good one) and some Obliterators. Obviously putting all that together effectively in a good balance and maybe leaving some of what I had said out is a good possibility. You may ask why these selections.
More Shots! More Shots!
Noise Marines, chaos obviously need the shots and without knowing the new rules, I figure there is going to be some psychic power that is massively powerful like the SW one that could involve Initiative tests. In turn making the Noise Marines maybe favored a little more than Plague Marines in tournaments. IF there seems to be more spaced out troop choices, the blastmaster maybe one upgrade to leave behind. Although I've had minimal experience with it, it has really never made that big of an impact, usually scattering too far to do damage. Depending on the toughness and armour save of warriors, it still might be a good answer to Nid warrior armies. Power Fists are a must, too many MCs to not have a lot.
Chosen, Outflanking the Infinite
According to my Nid friend, Gaunts will always have Without Numbers rule having a troop choice consistantly spawn in the back of the Nid players spawn point after dying, its easy picking for him/her to take objectives near his/hers deployment zone. Now with outflanking chosen in a rhino (havoc launcher maybe?), that could help out with that problem. I would probably choose to kit the chosen out with all flamers and power fist or 3 flamers, 2 meltaguns and power fist for some versatility.
In general having 4-6ish Rhinos all with Havoc Launchers will do damage even some serious if combined with Blastmaster shots on the first turn. That will help out a lot in thinning out the possible large numbers of Tyranids in the beginning turns.
Slowing the Mass Charge
Lesser Daemons could be extremely helpful in tying up key enemy units before they hit yours. Getting that extra turn to shoot with any and all of your units is very important. Especially against MCs because of the Invulnerable saves. A Nid player could get extremely annoyed possibly getting their MC tied up for maybe 2 turns, giving you the extra time you need to shot at the little buggers and get ready for the big ones.
Everything else speaks for itself, Obliterators, best heavy support choice available and DPs, maybe not exactly Lash DPs, but DPs in general.