Johnstone has been a key factor in Villa’s rise to third in the Championship, having conceded just one goal and kept four clean sheets during their current five-match winning run.
The 24-year-old has spent the past year as No.1 at Villa Park while on loan from Manchester United and Bruce will try to sign him permanently in the summer.
Any deal would almost certainly depend on Villa winning promotion but Bruce said: “We hope he will be our keeper for the next five years. That would delight me.
“Sam is a big tick as far as we are concerned. Whether we can do a deal, we will have to wait until the end of the season.”
Bruce has been delighted with Johnstone’s form and impressed with his development during his year at Villa.
After a shaky start, the former Walsall loanee is now one of the first names on the team sheet. Johnstone’s importance to the cause was demonstrated last Tuesday when he made a string of saves before Robert Snodgrass snatched a late winner for Villa at Sheffield United.
“Certainly you can see the difference in Sam from a year ago,” added Bruce.
“From the moment he walked in the door, you could see him physically develop and grow more confident and get used to playing week-in, week-out.
“He looks a very good goalkeeper at the minute. We are delighted for him – after a difficult start for him. He wasn’t everyone’s cup of tea to start with. But the more he has played the more he has matured and developed.
“He looks the real deal at the moment and that’s the benefit of playing.
“He has learned more here playing this year than he has in the last five.
“There is no doubt training and working with great players helps but nothing beats playing the game in front of 35,000.”