After running "aptitude update" and "aptitude safe-upgrade" on my Wheezy boxes, I find I have TWO kernels installed. One of them, the new patch for this "Meltdown" problem, does not boot. It hangs. Fortunately, they were smart enough to keep the old kernel and that still boots normally.
Why would it be incompatible? Could there be missing dependencies? Or could it be that the CPU is very old? (Intel E8600 -- yes, from 2009, but at least it's a 'hybrid' motherboard that takes DDR3 memory :)
Since Wheezy loses even long-term support in May, I guess they won't put much effort into fixing this. But I like my old Linux boxes. I hope there will be a kernel that they can run?