IMO, if you deploy on Friday, you are promising to be available for fixing it on Saturday... which makes it not really a Friday in the sense in which it's meant.
Don't deploy when you won't be around to support it is a better description; but it doesn't roll off the tongue as easily.
If it has the potential to take down your site? Unless you have someone who can fill in for you, absolutely.
Really, it will come down to a cost/benefit analysis. Are your chances of the site going down due to being hacked over the weekend higher than the chances of a last minute update taking down the site?
The answer is almost always no (much to a sysadmin's chagrin). If the answer is yes (i.e. another heartbleed), then you are probably going to be working through the weekend anyways.
Don't deploy when you won't be around to support it is a better description; but it doesn't roll off the tongue as easily.