One of the things I prefer in GW1 is the low level of different currencies. The constant adding of new currencies in GW2 is one of the things that brought me full circle to the original.
It's the price to pay for having horizontal progression. The problem is that without those currencies, there would be no boundaries into just buying everything upon the release of something.
That means that content becomes optional and only rewards more of the same, which means that next time over something new releases, people can just insta-buy it again.
To avoid that, you introduce a new currency that you can only earn by doing specific content (aka the new content) and earn the rewards in this way. While GW1 has significantly less of these currencies, there are still quite some in the game (for example, Medals of Honor, Zaishen Coins, Armbraces, Hero Armor etc) and should the game have been in development for longer, we would probably have the same issue here. GW2 has been in development for over 12 years (after launch), whilst the active (with the exception of the Live Team) development of Guild Wars 1 after launch only was about 2.5 years long. Now, that has always been a terrible shame in my eyes, they should have increased the studio to support both GW1 and GW2 instead... but that is another story.
But with horizontal progression, it's very hard to avoid introducing new currencies. And GW2 is the extreme in that, but they've finally started working on that (e.g. Unusual Coins being re-used in expansions, and when a new expansion drops the existing Unusual Coins become Ancient Coins). But, the same issue exists here: if they release new rewards, unless they want people to just instantly buy all of them, they're going to use a new currency for it.
not with GW3 in development
While GW3 is most likely in early development, I highly doubt it has passed pre-production. From what I could gather from that investor meeting, it was a panic-induced reply and not really "GW3 is fully in development, going to release soon". I would expect that even if it is currently in development, it's still going to be 6-7 years before we see a release.
While there was a gap of 5 years between GW1 stopping development and GW2 coming out, I highly doubt they would risk killing off the cash-cow that GW2 currently is (it's still one of their most profitable MMOs), so I would expect to see development on GW2 going on for many years.
GW1 getting new content is out of the question, not on the table at all. But I still suspect some improvements might be coming still, as long as the effort required is small. Stephen loves the game as well and I have no doubts that he is going to make a lot of changes, but I think most of these will be behind the scenes. But I do expect something to happen at the 20th birthday.
Best of all, Stephen getting to work almost fulltime on GW1 means that the servers aren't going to be shut down anytime soon.