Schumacher, 45, suffered a near-fatal head injury in a skiing accident in Meribel, France, on December 29 last year.
It has been two months since the family relayed any information on the sportsman's health. Their silence has led fans and commentators to fear the worst.
Gary Hartstein, a former F1 doctor, said: "I'm quite afraid (and virtually certain) we will never have any good news about Michael. At this point, I rather dread seeing that the family has put out a press release."
Writing on his blog, he added: "I can conceive of no possible reason that Michael's entourage, understandably extremely protective of his and their privacy, would not tell his fans if significantly good things have happened." Roger Benoit, a respected and long-serving member of the F1 media, said: "Slowly, everybody is really worried. Grenoble and the family have been silent for weeks. Why?"
Schumacher's manager, Sabine Kehm, last issued a statement on April 4.
It read: "Michael is making progress on his way. He shows moments of consciousness and awakening. We are on his side during his long and difficult fight, together with the team of the hospital in Grenoble, and we keep remaining confident."
She has been criticised by some for failing to release more information but in the past she has said this is what he would want.
She said previously: "Michael Schumacher is in a coma and cannot decide what is reported about him.
"We, of course, know how he deals with such things and try in his interest to handle these matters for him." Since these statements there has been no news. This is the longest period of silence since the accident.
It will be 23 weeks ago on Sunday that Schumacher suffered his life-threatening accident while skiing in Meribel, where he owns a chalet.
Doctors began the process of gradually waking him up more than 18 weeks ago.
Ms Kehm has said it is "very hard" for his loved ones to comprehend how the racing car driver could have been so catastrophically injured in such a "banal situation".
The accident occurred just over 14 feet from the edge of the ski run in a small, rocky off-piste area.
He was skiing with his 14-year-old son when he lost control after hitting a rock. He ended up smashing his head into a boulder 34 feet further down the mountain.
He is receiving round-the-clock care in intensive care in Grenoble University Hospital.
Corinna, with whom he has two children Gina Marie, 16, and Mick, 14, has remained at his bedside.
In February, French investigators closed the official inquiry into his accident, ruling out any criminal wrongdoing.