In terms of certification, TKD stylists of 1st degree black belt or above today subscribe to one of four options.

    1. Become loyal to either WTF or ITF / ITF (2)

    2. Be apolitical and join a third group independent of WTF/ITF politics.

    3. Get certified by both WTF *AND* ITF.

    4. Do ITF style movements and training and get certified WTF.

In reality, the trend now is to go back to the roots and finding an eclectic combination to be an all around martial artist who can adapt/fight to different situations. Aside from politics, it is what General Choi s ITF once envisioned. The trend is definitely moving towards recovering what was lost from factions of different TKD styles before WTF rules and watered down TKD.(eg. Moo Duk Kwan used to teach Jook-Do, a bamboo sword as part of its curriculum) Also TKD is also finding some other ways of being effective in martial art techniques than emphasizing powerful linear kicks which does a  number on your knee joints as you age.

Two ways of this approach are: One,  learning other styles after getting black belt in TKD. This makes acquiring the black belt in the second, third, or fourth martial art a lot easier since you understand the fundamentals and have a base of reference to compare much more soundly than a lower ranking color belts who ramble more about theories than a practicality(everybody in MA does this once, yours truly included). I have encountered more and more people black beltss in multiple arts in their 20 s nowadays than before. And most acquire it after attaining their black belts in one art first.

The other way is to learn other styles incorporated into TKD (The way I was taught). As a black belt  only in TKD, one might not have the quality skills at the level of someone who only knows the other art. But the all around skills do help.

Or train in both WTF and ITF styles together as offered by Grandmaster J. H. Kim(Boston) or Grandmaster Hee IL Cho. Both schools are probably in the top five TKD schools in the nation for their quality instruction and number of students (usually 1,000+).

The challenge now lies at a crossroad at this point.  The splintered out TKD groups could get together again which, in practicality will never happen. One way is to make TKD artists aware of the shortcomings of the art and complement with cross training. Or be proficient in other arts. What is seen nowadays in TKD is over-emphasis on straight line kicking, and straight line movements and almost a total lack of groundfighting.  But the biggest detriment to growth of TKD is the limited knowledge/quality of the  post first generation
instructors.   There are some inflated black belts in martial arts including TKD instructors who are unwilling to show how much they do not know. Some teach a wide range of moves without foundations. Teaching effective joint locks, throws, sweeps are OK; but you have to teach the students how to break falls or roll. You also have to explain the theory & principles behind it of how and why they work. These are essential for recoveries and compensation when mistake is made both in offensive and defensive movements.

Some of the awesome masters I have been fortunate to get training from and work under in the past, will actually invite another well known high ranking BBs in another martial art or a fellow grandmaster in another MA. The master instructor tells the students to diversify their learning of the martial arts once you achieve black belt and also to attend numerous seminars.  What one particular 9th degree  TKD grandmaster achieved from this attitude was more respect from his students. He actually told the students,  I am not proficient or don`t know this art as much as the guest instructor, but I want you to learn to become a well rounded martial artist.  The guest instructor was a 6th degree black belt in judo and came on a regular basis to special train the black belts in the 9th degree grandmaster s TKD dojang without extra cost to the student.

In Korea, there were several martial arts groups after independence from theJapanese. All wanted to get recognized.  General Choi being in the military had the dominance and called it TKD, and tried to unify all factions into his style called Oh Do Kwan and ITF. He failed and another rival organization WTF led by
Dr. Un Young Kim, with backing from the civilian government succeeded in unifying all the TKD factions. General Choi courts South Korean government to support his organization, but is turned down. He then courts North Korean government, gets support but also leads to the weakening of  his ITF organization by massive departure of his subordinates.  WTF takes this opportunity and takes the void left by ITF and leads as the  official governing body of TKD . 

The WTF emphasis is on tournaments, ITF on traditional TKD in sense of the martial art . NEITHER IS BETTER THAN THE OTHER. Most students are not really interested in the politics unless blindly swayed by their instructors or are not exposed to both styles.  The future trend for TKD appears to be growing into a versatile martial art, which Gen. Choi achieved briefly in the military in the  70s before its decline. But whether WTF/ITF or other TKD organization, it is slowly getting there. The trend speaks for itself; just about all the WTF Korean gold medalists in the Olympics had multiple BBs in other martial arts; and year after year, more and more weapons and hapkido techniques are demonstrated by the WTF demonstration teams.

Note to students who feel their TKD style is  superior  to other styles. Select REPUTABLE schools different from your TKD style(with history of operating 10 or more years in one location, the longer the better) and ask if you can participate in their training and/or sparring. You will find everything has pros and cons in life, including different TKD styles. 
by W. Rhee