That info is almost 2 years old, and it's out of date.
Now there are only 4 retail forex brokers in the U.S.
This graphic is 9 months old, but it shows the 4 brokers currently offering retail forex trading in the U.S. and their respective shares of the U.S. retail forex market (as of June '17). Their market shares have not changed dramatically since then.
Yes, it's a trend.
Back in 2009, there were 24 retail forex brokers operating within the U.S.
Here is a post from August 2009 listing those brokers.
(Use CTRL and your mouse-wheel to enlarge the table.)
In 2010, the CFTC began to fundamentally change forex trading in the U.S.
Sounds like Obama, doesn't it?.
You can read a brief history of these events here:
Foreign currency trading will continue to exist in the U.S. (and elsewhere in the world), as long as sovereign currencies exist. In other words, until we have a One-World-Government and a One-World-Currency, there will continue to be separate, national currencies competing with one another -- and that's the genesis of currency trading.
If the profit potential of currency trading attracts you, and if you find out that you have an aptitude for this market, then you will probably want to participate in it, regardless of how it evolves over time.
One caveat: As a complete beginner, you should ignore (for now) the possibility for trading through offshore brokers. Trading offshore adds another layer of complexity to trading that you don't need at this point in your forex trading career.
Choose between Forex.com and Oanda (the two largest U.S. brokers, and most likely the only ones you can afford). Open a demo account with one (or both) of them, and find out through experimentation and practice whether this market is something you want to get involved in.
If and when you get good at this stuff, the forex market will still be here.