But it is just that - a coincidence. My guess is that these movies are being shown in the spirit of movie in theatres "The Day After Tomorrow" (think that's the name).
This "Post Impact" moving coming on SciFi has been advertised for a few weeks now, at least as long as the "Day after tomorrow" stuff. So, no, I don't think so. It was made probably in the last few months, and not in RESPONSE to "Day after". "Post Impact" is about what happens AFTER a meteor impact, apparently. I've only seen the quick ads and trailers for it so far. I'll be watching it though, just for good measure :)