I happen to have attended the ATW (Aerospace Thematic Workshop) twice in 3 years, so I can give you some first insight.
I do not know precisely when plasma flow control was first experimented on, however this field gathers a quickly increasing amount of researchers around the world.
The reason for that is that, before, people could use continuous DC plasmas (not practical at atmospheric pressure because of filamentary structure of the discharge, and strong thermal instabilities that always lead to an arc, that is a power-consuming and ineffective discharge) or at best DBDs (dielectric barrier discharges: you have two electrodes, and between them, an insulator. When you switch the voltage on, a discharge will "creep" on top of the dielectric, and ionize the air, without transiting to arc because current cannot pass).
But today, you have nanosecond high voltage discharges: high voltage rise time allow for high currents, and nanosecond limitation of the discharge allow for avoiding the transition to arc. This way, you deposit a lot of energy in the flow, and you chose which way the energy will be deposited: thermal energy with very fast heating (fast gas heating...actually the topic of my PhD thesis!), vibrational energy, or slow gas heating (as in arc discharges).
And with very fast energy deposition into thermal energy, you get shock waves, which even in hypersonic flows, can do something to the high-enthalpy flow, while keeping the energy requirement low enough to be embarked on a flying vehicle. And this is a great step taken forward, that used to be really impossible in the past!
One application of plasma actuation is to mitigate the noise produced by reflected shocks in supersonic aircraft air inlets, and some very recent results show you can indeed tamper with instabilities that generate noise, and damp them.
But as you asked for an honest answer, I would say this research still needs at least 5-10 years before ANYTHING practical can be proposed for industrial purposes...and possibly more.
I hope this could help you get more insight into this field!