Well, THEY STILL HAVE GROWTH IN MEXICO as long as it's above Zero %.
But the stats show that might go away. Surely, they are running out of kids willing to be baptized or forced into it.
I can imagine the retired English-only JW's are such a minority. Most probably could go to Spanish language congregations. They might even like going to Spanish if they don't speak the language, just sitting there like bumps on a log as usual, but with a language-barrier excuse.
If they close English-only, it's a money thing. The retired JW's probably give minimal amounts to keep the congregation expenses at bay, but not much toward the worldwide work.