I mean, it's possible that they are currently doing all the refactoring and cleanup that has been neglected in previosu years. This would also explain, why they are not able to produce more content at the moment (and why it's so costly). If this is actually the case, then there might be light at the end of the tunnel, i. e. future additions to the game might become less complicated and less likely to produce bugs/regressions.

Also, why would GW3 lead to players abandoning the franchise? This is not what happened with GW2, or did it? I always thought that a lot of former GW1 players are now playing GW2 and some maybe even still play GW1.

My theory is that whatever ArenaNet had in the working during IBS was not good/finished enough or too far off from the current francise that NCSoft pulled the plug and "condemned" ArenaNet to continue releasing content for GW2 (with a much smaller development team on a code base which is increasingly hard to maintain).