It is impossible to say at this stage, but most stroke
sufferers make a pretty good recovery. My mum had a massive stroke a few years ago and has been in a nursing home unable to talk or move properly ever since. She still knows who we all are. That said, hers was an extreme case. My old boss had a stroke a few years ago - same symptoms as you have described, and now it is like nothing ever happened to him. Strokes are difficult to predict so keep thinking positive. He may be completely OK next week. The crucial thing with a stroke is that the earlier it is treated, the better the chances of very little long term damage. When he comes out of hospital, an asparin a day will keep the blood thinner and reduce the risk of another stroke.
As for memory loss
, it depends again on what part of the brain has received the stroke as different parts of the brain control different aspects of the mind and body. Just keep thinking positive and hope for the best. There is nothing that you can do until you see the doctors tomorrow. I know it's tough but time is the key now. They will know a lot more in 24 hours than they do now.