It won't last forever, not unless it becomes more complex. Combat is very simplistic, with most of the strategy being in how you approach your target rather than how you attack them (click for hurtmaking, no zone-based damage, etc). Gear is also very simplistic - four effective weapon strengths, three effective armor strengths. Loot is poorly spread out - only two tiers of chests means you either get geared or you get "junk". Maps cannot be varied enough to remain interesting for the long term - once you learn where chests are, you know where to go forever, and that map gets somewhat reduced in terms of effective complexity.
In short, the mod has potential, but it really, really needs depth in order to survive. I'm not entirely certain the depth it could use is even available in vanilla MC.
Really? I find Minecraft PvP to be very complex. I find myself doing mind games without even thinking about it - for example, I found out that my teammates generally pull out there bow if they see me pull out mine, so long as they are about 6+ blocks away. So, I pull out my bow, shoot it right away, then rush towards them while they are trying to take our there bow and use it on me, giving me an effective 3+ hits before they can retaliate. Little mind games like that help a lot.
I also found myself about to fight someone stronger than myself at corn, and by the way he was acting when he saw me, I could already tell how he'd try to fight. I pulled out my bow, got in 2 hits, then I rushed towards him, not to use my sword, but to make him rush back at me still thinking he was stronger despite the lost health. I pull out a flint and steel and start backing up, planted fire on him the moment he was within range, then continued to chase him with the sword while he was low on health. I took no damage that battle.

Believe it or not, I find out how somebody will try to fight me based on how they decide to approach a battle with me. Had that guy acted differently, I wouldn't have done quiet that strategy. Against a stronger opponent, they would have jumped to the side as soon as they saw I didn't want to sword fight by backing away, because that means I'm about to use a bow/flint and steel. They would have went around the fire, hit me into the wall and made it almost impossible to run away, and that would have given them a huge advantage over me.
I could argue farther on your other points, but I'd rather not drag this any farther off topic.
Edit: Also want to mention that I'm not saying Minecraft has the most complex PvP system out there, there is far better ones, but it's a lot more than some people make it out to be. (it's not just point and click.)
On topic: It could be in a lot of places in four years...a lot happens in four years. Personally, I like surprises, I'll wait and see.