Relics will be upgradable, and not necessarily BIS for all of eternity.. Truth of the matter is people are raving about how easy the quest is, and how little effort it requires, yet a good chunk of these same people probably don't even own one.
Do remember that while yes, quite a lot of people have built a few, there are also more then likely a huge number of "new" players that will look at these relics and go "wow" for quite a long time. So yes they probably will be the best in slot for a few level caps. I won't be overly heartbroken if an equivalent such as something similar to an Empyrean/Mythic pops up, and so it should - I would love to have options. However people have to remember that the people that played til last save, built a few relics, defeated all the content - will still be king of the mountain and in a smaller % for some time considering the server population increase for new/returning players.
Before the last save, there were a lot of relics around the place, but you have to remember that those very people- the ones that stuck around til that point will be the more "hardcore" or "determined" players.
So my point? Yes they are easier to obtain then XI was (partly because instead of having to get 18 people to build 1 person a relic efficiently, you can take 8 people through the quest), however the advantage with the current XIV relics is that there is actually a heavy weight on skill rather then flat out grinding beastmen coins til the end of your days.
Anyone with a deep pocket could obtain a relic in XI. However in XIV, there is a benchmark of skill required (17m dungeons/garuda/ifrit). While some may say it's a walk in the park, the majority of people find dungeons and ifrit especially challenging. So comparing XI to XIV isn't really a viable comparison here, as farming currency does not dictate skill level. It dictates persuasion to get people to work for you, it dictates how deep your pockets are, and how lucky you are with RNG. That to me is not worthy of a relic, but defeating a difficult boss (such as Ifrit extreme) does.
I can assure you that Ifrit will probably just be the beginning of this path. When the game reaches it's last cap, I expect the final boss required to upgrade your relic to be next to impossible, less linear (as the current primal fights are), and introduce a much smaller percentage of fully upgraded relics.
If I am not mistaken, Yoshi said in an interview that relics will be upgradable. While they may continue to be best in slot for a while, the next tier above them will stem from the relic. (ie Excalibur will stem off the Curtana after fulfilling a quest requirement - etc) This includes a graphical change to the relic also...
So my understand of what their plans are - is simply that the current relics are the base item of what is to come.
In summary, they may appear to be everywhere, and while some people are 7/7, you have to remember that the players that are currently still playing, and currently own a relic, will actually end up being a small percentage of the population on the server come 2.0.