Pal, those predicted grades mean nothing except that he isn't currently working hard enough to do well in his GCSEs. It's a very common year 10 problem, particularly among boys it seems.
If he's getting Cs and Ds without doing any work, he could get As and Bs if he does some. Maybe this report will be a wake-up call for him.
On the other hand, maybe it won't. Maybe he is not interested, or maybe he isn't ready to knuckle down... Or maybe he's one of many young people who learn through doing rather than sitting still and listening, who aren't very well served by our secondary school system. Lots and lots of kids like this underachieve at GCSE level, but then find motivation and pleasure in learning again at a Further Ed (FE) college.
Nothing at all is determined by his GCSE results, except his confidence. And perhaps admission to a handful of top-rate universities - but not necessarily even that. If he wants to go to university, it's his level 3 qualifications that count - i.e. A levels, BTEC higher diploma or Access to HE course.
If by any chance he does very badly in the 'real' GCSEs - fewer than 5 grade Cs - this will slow down his progress to HE (if he still wants to go). He will certainly get a place at an FE college, but not necessarily on the course he wants, and he will need to prove himself. If he doesn't get English and maths GCSEs at grade C or above, but wants to progress, he will need to retake them.
If he's still not ready for study, the door still isn't shut. It is never shut, since he can apply to university as a mature student at any age, if he wants to.
It is the wanting that is key. He won't do well unless and until he decides he wants to work hard.
As for your survival, well it comes down to detachment again! Hold on to the thought that he's not ready now, but there is still time before GCSEs, and that even if he's still not ready by next summer, there will still be lots of options when he is. You can support him by not panicking - which will add to his panic - and by helping him believe in himself. Say things like "Well, just think what you could achieve if you put your mind to it!"
You already know some of my experiences with my own DS. He underachieved badly in his GCSEs (4 grade Cs and a B) messed about for a year, and then found a course he wanted to do, and is now doing very well and is likely to go to uni. He just needed to decide that he wanted to study.
As well as my personal experience, I have taught for 4 years in an FE college and 4 in a university. I have seen countless students who did badly at school go on to do well. Don't despair! :)