The argument with losses through mergers is a good one. Just because something changes (battlekeeps, guild city spots, names, trader market and prices etc.).
But open pvp is not. Assuming people prefer populated servers over a small "dominated" oligarchy server of course...
First, if you follow my suggestions everything possible on Fury would be possible on the merged server too.
Second, there is not really much open pvp left on Fury. This will not change with a merge imo, though. Only a change in the open pvp system can help here. The duelspots are empty. There is no Tortage pvp. 59 and 79 minis are not existing anymore. If you just merge without adding a working consequence system and more stats (like achievements, renown etc.) you might get another temporary boost, that is drained fast and driven off as happened since release.
What might change here, if they can give changing rules or instances with different rulesets, is, that they could actively encourage people to play more between 16 and 80 and work on a consequence system step by step (or gradually make conan harsher as people progress, making each level tier fun and worth to stay at again), instead of grinding pve at 80 for pvp. This can actually work now, with pvp gear revamp and if they add more pvp gear, especially at pvp0-3.
And you have to admit too, that there is a risk or disadvantage, for the open pvp crowd, because people will not be "forced" anymore to play pve in pvp enabled zones. That is why you should give different pve rules there too as well as change the open pvp system to make it more fun for the loosing side. Such a merge would be critical and risky, so these factors have to be tested and thought out thoroughly before making such a move. Far more than just the technical possibility to be considered (one reason why people advertised trying out the different instance rules in addition to normal rules for events or on crom for the pvp quests. If it does not work out as intended, you can easily take back such changes or adjust the rulesets there without changing existing systems and rules people are used to). That's why developing additions instead of replacements is so important imo.