Absolutely should have world PvP, but of course it needs to be well thought out and players need to understand an evolution of a feature. The vision and intent of the dev team for world PvP needs to be clearly conveyed to the community so expectations can be managed. Mechanisms should be in place to mitigate frustration to players that are either afraid of world PvP or who are way under powered to go up against predators. However I strongly encourage and enjoy titles that have PvP mandatory areas.
A key component lost in modern MMOs is unique and exclusive. Not every player has to be entitled to every single thing if they aren't willing to take on the risk for it. No risk it, no biscuit.
If PvP will be gated behind certain areas, or flagging features, then players who refuse to PvP should not be entitled to reap the same benefits. If PvP will be rewarding anything at all that is... E.G., A zone that has mandatory PvP enabled, you cannot enter the zone without being subjected to it, has X amount of content in it, can only be obtained by those willing to throw down. That doesn't necessarily mean every zone needs to be PvP mandatory. However the world needs to feel risky, I personally far more enjoy my experience when there is threat lurking and I am not 100% safe. It is also an element of social interaction, with threats lurking around the corner, players should communicate and work together to combat those threats.
With that being said, of course there should not be reward for a high level/powerful player to gank a lowbie. Could also level balance based on zones or debuffs to players that engage lowbies.