Is MIL-STD-1553 still used in modern aircraft?
MIL STD 1553 is alive and still in use.  Backwards compatibility will keep it around for some time.  Not only is it used in aircraft but also on spacecraft.  

It tends to be used for control applications and lower data rates.  High volume data, for example from sensors, will employ different bus structures.  Many control, communications and guidance applications can readily be accomplished with 1553.

Having said that, I cannot say whether it is right for you application, as I know little about your application.  Noise, data rates, latency and other factors may cause you to look at different interconnection architectures. There are many competing bus/LAN structures.