BIS has been criticized by their own Community on every release since OFP on the buggy state of this series.
I think this time around they've weighed the pros and cons of delaying release and I think it can only be a good thing. I'm pretty sure the move from PhysX 2.0 to 3.0 didn't come without hiccups especially being new to this Dev.
I'm also more and more convinced that with the delay of DayZ, Rocket figured there was no way to use the Real Virtuality 3 Engine in it's current state. I'm wiling to bet he's either:
- Working with the current engine but in a manner that can be ported directly over once ArmA3 has been released.
- He's dropped working on Real Virtuality 3 and is actively working on the new engine.
You also have to remember that this engine will likely power their VBS Software so it's pretty important to get it right.