Let's say that the next Expansion is actually Cantha. I'm also going with Tengu as the fan favorite for a new race and a race that fits the Cantha story best since that's where they're from, so we'll just assume this is the one we get.
What if, rather than building them up like the other races they're an instant 80. Skip starter story, make part of character creation to be to choose which Order they were a member of, then skip most of the low level story, possibly even skip straight to making the pact. Or make the first three starter story chapters all level 80.
The Dominion of the Winds could be introduced as part of the expansion as a level 80 zone, instead of a standard starter zone. But the race itself is a merged instant 80, extra character slot and new race all in one. The expansion comes with one free Tengu, but it's also possible to purchase a Tengu for Gems, if you purchase a Tengu you get their home city and the Dominion of winds, even if you don't have the expansion, you just can't do the story parts that take place there (except Tengu starter story, if there are any.) You don't unlock the ability to have Tengu, you literally purchase the ability to make a single Tengu. It might be too complicated for them, and I don't know how deleting characters would work, but I'm not a programmer, so it's not up to me to flesh out all the bits.
I know the concept of new races comes up all the time, in fact someone else just started another new race post just before I finished this, and also Tengu, and that they said they weren't going to, but I don't believe I've seen this particular idea before, and an expansion needs a hook. It's not an unheard of concept to introduce an auto max level character. This would also allow them to do some old things they had intended, while also moving forward. Obviously the biggest issue with a new race is voice acting. All the lines of old material would have to be redone, twice. That would be a pain, and that might still negate the whole thing. But I think it might be worth it if we have to pay every time we want to make one. They could also just make it so a Tengu literally starts at the expansion, whether you have it or not. If you want to play the personal story, HoT, PoF or any of the previous LS chapters, play it with something else. I'm not sure if that would work either, but it's a possible option.
Tarnished Coast - Ranger (80), LB/S-D, Eagle/Wolf, Signet, M/S/NM |Daredevil|Ranger|Guardian