Lots of shows take winter breaks these days, as it allows production to catch up while avoiding reruns, building anticipation for the spring premier.
That said, most of the shows for which that model works best are serialized dramas and adventure series. Think Agents of SHIELD, Once upon a Time, or the Thursday night dramas, which don't air reruns at all and instead have entirely separate fill-in series take the timeslot during their breaks (like Agent Carter). The Muppets is somewhat serialized, but so are most comedies these days, and many of them do air reruns during the interim, as comedies are more traditional rerun friendly than heavily serialized dramas.
So they promoted "Swine Song" as a midseason premier, but comedies aren't typically perceived really having that sort of break in the first place, between the less-serialized perception (though they often are rather serialized in practice) and the traditional airing of reruns (as opposed to not airing at all). As such, I don't think anyone can really say that it affected the rating one way or the other (and certainly not after one episode).
What works in The Muppets' favor is that a) it's ratings are largely in favorable demos, that is while the overall viewership could be higher, those that are watching are largely in the age bracket advertisers like to see, b) it's been ABC's strongest new comedy this year, c) it's owned by Disney outright, with a property with outside marketing potential, and d) it does well in delayed viewing platforms (DVR, in demand and Internet streaming), all of which are not only increasingly important parts of viewing, their rise has actually made the traditional rating less important than they used to be. (Lots has been written about the effects of this sort of viewing on the industry as a whole.)
So, while a night change is possible, even likely (Would be a good fit for Wednesday), I think there's a better than average chance that The Muppets gets renewed.