There will be new features, at least where the ME is concerned as you have guessed. Possibility for anything more isn't being discussed publicly for now since nothing has been nailed down (that I know of, I don't make the decisions).
I wouldn't worry too much about the avionics. The FC series serves the crowd that isn't into exacting operation, but there's nothing wrong with meshing DCS and FC. Basically, if you consider facing off with a fighter, an FC fighter and a DCS fighter would appear to fight about the same; in fact a DCS fighter will likely have advantages in avionics.
But in the end, it all depends on how you want to fly, and so you'd join an appropriate server or crowd I imagine
I'm hoping they will add some decent features with FC3, the just having the triggers of A-10C in FC is fine by me. However, I am somewhat worried that without some improvements to the avionics of FC3 aircraft that the sims won't mesh well together.
Take the radios for example. Radio frequencies matter in DCS. You gotta tune to the correct frequencies to contact ATC, JTAC, to hear (or not hear) AI flights, and so on. FC2 had what is considered to be "easy radios" where everything is tuned to the correct frequency automatically. So with AI flight to communicate with the player there is bound to be a constant and unavoidable noise of AI chatter. Granted it all depends on the number of AI in a scenario, but having no options to switch frequencies would really suck.