Since /world was added, we've got /portals and end gateways (added in 2015 and late 2016 respectively), which provide a fine alternative to a trading/pvp dimension. Portals and end gateways - which are very common - are used by basically everyone to get to spawn.
I imagine that end spawn would become the new trading/pvp area. Like /world, end gateways provide a safe one-way means of getting to the public trading/pvp area, and a safe one-way means back home.
This will also negate the /pvplist and /pvplist subscribe commands, which in my opinion are OP. It makes piracy or surprise attacks basically impossible as you can instantly leave as soon as someone joins. For a server named SimPVP, PVP is extremely rare and easy to avoid.
The only issues I can imagine are as follows
- It'll become harder for new players to trade for late-game items after a few hours of playtime - First of all, good. Second of all, people can travel from end spawn to overworld spawn with a portal, and trade there.
- End gateways are easily trapped - This is true, a simple TNT minecart trap will instantly kill anyone who enters a gateway, and the gateways would be easy to camp. Being able to predict where someone will appear in the trading/pvp area is obviously bad, hence why /world teleports you to a random location (and used to teleport you to a small pvp-free zone). The solution to this could be a plugin which teleports you to a random location on the main end island when you enter a gateway, rather than the same set location.
- You can easily escape without being 50 blocks away from an attacker - I guess this is true, maybe a pirate/scammer/pvper could cover the middle end portal with obsidian beforehand to make escape more difficult. This said, escaping /world is already incredibly easy by simply flying away and using a chorus fruit or enderpearl to get far away, so not much would change here.
- edit: End spawn wouldn't change every 2 months - This is a novelty we all like about /world, and it'd be a shame to see it go. Maybe end spawn could be changed every 2 months, or something.