Infantry has been the primary focus yes that much is obvious given how many updates they get, that said there is no doubt that there is expansion in mind with physX coming. While infantry are gaining ragdolls vehicles are also getting proper suspension and so on, RTT is another more vehicle priority focus unless we will be carrying mirrors into urban zones to look around corners without exposing ourselves to peek.
While it would be nice to have fully interactable cockpits, advanced weapon systems, tracking systems, dynamic arming capabilities, very complex damage model and so on I just don't see that happening as it takes a LOT of time, that said simply giving us the capability would do well enough. When you look at the effects that come out of the capabilities the pieces fall into place to making things more complex..think about it.
In OFP armor interiors were possible and did not interfere with the players sight other than what they were meant to, in Arma1 we saw that HDR caused intense issues when looking at the inside of the Stryker, and while HDR has been getting improvements we can still see, especially inside structures, that it would still interefere. Now what is another arguement for lack of vehicle love?..well what is the point they say. With RTT coupled with thermal imagery especially if (and I hope) environmental thermal takes a fairly high priority, we now have a purpose to have interiors where HDR would not screw with our eyes. It sounds useless but this increases immersion drasticly but also potential.
In the end we all want Arma to be something different, two most distinguished sides want it to remain as is, the other side wasn't mistress-like hardcore, obviously BI can't please either party to the fullest but by taking things 'easy' and providing us the knowledge and abilities to use the upgrades to further our agenda's, in a way they can please both.