Warnock was dismissed in January, just months after winning promotion to the Premier League, to be replaced by Mark Hughes who himself was sacked earlier this week.
Rangers are yet to win a match this season, after collecting just four points from 12 games.
And Warnock, currently with Championship side Leeds United, told the Independent: "I would like to wish Harry the best of luck filling my old seat in the dugout at Queen's Park Rangers.
"It was one of the achievements of my managerial career getting QPR back into the Premier League after a 15-year absence and I would be very sad to see them go back down after all the hard work the players, staff and myself put in.
"I have to admit there have been times this year when I have had to bite my tongue.
"I kept hearing the team were playing well without getting the results they deserved. But so were mine but we did win away from home three times.
"There was also the comment at the end of last season when my successor said after coming 17th - the same position I left them in - 'we won't be in this position again'.
"Unfortunately he was proved right. QPR have not been that high since.
"It was difficult to accept when I was replaced. Having met the mandate of keeping out of the bottom three we were about to make the signings in the January window we needed to head towards mid-table.
"Having kept QPR up I planned to retire and hand the reins over to someone else for a smooth transition.
"It is easy to look back in hindsight but I think Tony (Fernandes, club owner) might now reflect and feel that would have been a better way to proceed."