There have been some good things said here. I've been lucky enough to meet and spend time with some of the best guitarist on the planet. Malmsteen is one of them. I'll tell you this. All of them have one thing in common and it's not starting to play at an early age. Its a solid practice routine and an expert knowledge of music theory specifically related to their instrument. These things are taught by teachers and learned by focused students. If your not Focused FUGEDABOWDIT. I've been lucky enough to ask John Petrucci exactly what he does to be and stay that good. Do you know he has someone on the payroll that catalogs all the lessons in all the guitar magazines? All the time and has been doing this for YEARS and YEARS. He Cuts them out and Files them and the guy can recall them at any given moment, scan them and send them to John regardless of where he is on the planet. John puts an unbelievable amount of time into practice DAILY! Most People don't have or won't sacrifice anything else to make the required Time to be as good as him. Most people also don't have the discipline to practice like John does. I once heard Geddy Lee say. "This is my Job and Just like you, I spend 8 hours a day doing it 5 days a week". So My thought is YES you can be a virtuoso but it depends on what you're willing to put into becoming one. There is some truth to all the crap about muscle memory and age. But the real truth is that we are destroying ourselves and although we live longer today, we also age faster than ever now. Why? It all has to do with what you put in your body. You can over come that by changing your diet. Muscles lose flexibility when they become too acidic and when they don't get challenged. So if you drink Soda pop which is highly acidic expect to find limitations in picking speed and fret stretch ability early on. Water is about the most important thing you can change. Drink High Antioxidant, High Alkaline water that has micro-clustering (Google Kangen Water or contact me. I'm on it so is Steven Tyler and a grip of other pros). You need about 3 liters a day to flush the toxins out of your cells. And you will see a difference in a week. Then of course don't eat crap like fast food and you need to exercise 3 to 5 times a week. You need to practice Guitar DAILY though and if you have a finger exerciser....USE IT.
That's my Two Centavos.