A few important details:
Prompt attention indeed raises the probability of recovery from a stroke. However, all strokes are not the same, and no human being can promise 100% recovery. Nobody. People should not raise false hopes like this.
That being said, prompt attention is extremely important, and may indeed mean all the difference between recovery and nonrecovery–and will certainly determine the degree that medical science can help.
One important thing is to make sure that any elderly person living alone has access to one of the medical emergency devices. This will allow them to summon help quickly if they are still functioning. Ideally, elderly people who are prone to strokes should not live alone, as someone who has a stroke can then go quite some time before discovery.