Ah but that's the thing: Jehovah's Witnesses believe that only 144,000 people get to go to heaven, and the rest of us either stay dead or, if we're good, are resurrected bodily to live on a new and improved but still earthly Earth. Admittedly, I couldn't find many details of exactly how that will work (will people be immortal? Will new injuries heal automatically?) and I don't know, maybe only the people who go to heaven lose their disabilities in which case your argument absolutely holds.

As a Jehovah's Witness who contacted me privately (very politely) pointed out, the original title of this post was misleading in this regard, so I've edited it.