I'm not a statistician (though I took 1 course in my uni and also needed it for my Master research thesis...but still it's not my cup of tea. However, I did economics and I love it...so here are just some of my thoughts
1. I do believe in the midst of all those "random" price fluctuation, there are some "repetitive" patterns that doesn't arise due to chances. I see them all the time in my charts, whenever these "conditions" happened, there are usually a significant trend. The problem or challenge is how to exit timely as these trends are sometimes weaker than another. Hence, I do believe we can statistically find these repetitive conditions that are not due to random chances. Just like Google analytics, it tracks buyers profiles and buying patterns and by understanding their repetitive search or purchase patterns to predict what kind of advertisement would "suits" these users. Though most retail purchases may seem to be an issue of impulses, there is some "predictive" behaviours behind the sum of all these random behaviours.
2. As much as we often think that forex is so "unpredictable", it is still often governed by basic economic factors or market forces such as Demand and supply. It's the psychological part of speculation that fuel the volatility.
3. There are big players who dominate/dictate forex prices/trends and I believe these people's decisions are more often ruled by economic factors rather then whimsical and psychological (which most retail traders tend to react). I don't think they wake up one day and decided to sell because they "feel" like it. Since their decisions are more likely governed by forces of demand and supply (or fundamental issues), therefore it is possible to "see" a pattern behind every breakout or big movement made by these big players. Hence, RSI is a good indicator to use to lookout for these "pressure" points. Imagine if you happened to use the same "indicators" or whatever tools they use for their decision making, it's like "insider" trader whereby you have a close estimate of when/timing (not in terms of day and time but via indicators), whereby these big players are going to enter/exit the market.
Hence, in a nutshell, I do believe there is predictive value (if there isn't, then we are all gamblers here) in forex and usually the shorter the time interval, the "stronger" the predictive value. For example, which is easier to predict? To predict whether EURUSD prices will go up or down 1 year from now or 1 day from now? Of cos, it's much "easier" to predict the prices for the next minute than for the next hour. Hence, I believe if we focus on how much we can scalp out of the market at shorter intervals, we have a better chance of increasing our EA predictability because the longer we hold, the less certain we are about when the trend will start to change. Thus, most of my EA trade very frequently at shorter intervals.
However, from a position trader's point of view, there is also predictive value if you look at the market on a "bigger" picture. And use D1 and higher chart as reference point. Such trading method isn't my cup of tea because one need to have really large SL to stomach all those high and lows. And the larger the SL, the smaller the lot size, relative to your capital, you are able to trade "safely". Eg if your SL is 3000 pips and you only want to risk 10% of your capital, then you can only enter 1 lot size per $30k capital. I personally believe such method isn't "economical" use of capital for optimum return and if you divide the returns over the long holding time needed, it may not be really that attractive investment considering the high element of risk vs return.