Nostalrius will release a fresh vanilla PvE realm to fulfill the needs of these players.
https://forum.nostalrius.org/viewtopic.php?f=2&t=20231
They have also already posted details about the server, that player numbers will be limited to 2500 with a queue, how content will be deployed on that server - it will follow the same timeline as the PvP server - and that players will have the chance to relive a new fresh server start, which is also why a lot of people want to play there.
This second realm will benefit from all the upgrades applied on the current PvP server since its release, including general fixes, bug abuse fixes, anti-cheat features, and other automated systems making players' experience as delightful as possible while protected by mature and efficient-proved algorithms against exploiters. This server population will be limited to 2,500 players with a queue; it will be the same limitation as official retail servers back in 2006.
Regarding content release, it will follow the same timeline as the PvP server. Character transfers from the PvP realm will never be possible. As a consequence, players will be able to relive a new fresh server start: a rare and tremendous moment for everyone