I dont know if trance would evolve if there were no vocals, but I certainly hope so.
Nowdays I can't really listen to any good tracks unless its a dub or instrumental. I can't take tracks that have lyrics nowadays because they're just so boring and repetitive. I've yet to come across this year's "Vocal Track" ... just like "Satellite"/"Burned With Desire"/"Beautiful Things"/"Holding onto Nothing" .... and off that category.
Since vocal tracks are rising a lot ... (even if they're crap), i find no sense of music in it ... no actual production taken towards it. They all seem so rushed. For example DJ Shah's new track ... with Rene, felt like he had to finish it to keep it in the 'summer' zone. Bah ... useless.
I honestly wish producers would stop getting vocalists (with random lyrics btw) just because they can't come up with any melody.