While I would personally gain a lot by having the extra time, it's exactly how JackGriffin said.
Certainly, some more maps would probably be able to make it, and existing ones could potentially become a bit more fleshed out, but most of them wouldn't still make it in time (it's been proven time and time again), and at the end of the day this is a contest, albeit a friendly community one, but it has a deadline and everyone had equal opportunity to sort their shit out so they could deliver something by the deadline.
I know, as good as anyone else, how RL can be a bitch to fuck up your schedule and your ability to submit something, but that doesn't invalidate deadlines and the fact that there were those who had to go the extra mile to be able to release something makes any extension to be in bad taste, to not mention those who didn't even start anything due to the deadline.
For instance, I have been sleeping less during this week, and didn't anything else in my free time to be able to make it, even got earlier to work to leave earlier as well, so that I still had some good brain hours left before it started to scream at me to rest. Everything was going great, but some stuff out of my control happened which fucked up my own schedule, but it's my own problem, not a problem of the community which would require an extension like this.
Furthermore, let's take a step back and see how this contest went: it was proposed weeks before it even started, after all rules were discussed and sorted out, the contest would only start another week or few weeks afterwards, and then everyone had exactly 6 weeks from there. This contest already lasted more than 2 months, if not 3 already in practice.
I personally proposed initially for the contest to end on the 14th, since it's a Saturday and ending it in a business day sucks a lot. But papercoffee set the date and no one else budged, so that's that, that's the deadline.
And personally, I did the extra effort as well on my side, a bit like JackGriffin did, and I don't really care about winning or anything, I did the extra effort because I want to submit a map as part of the contest and not just as an addon after the fact.
So if I manage to finish mine today, cool, if not, then that's that, and I will have to live with it, and the effort the others put into releasing something on time should not be penalized by extending it.