Nobody can say for sure yet, but I doubt it'll be around very much longer.
If you're looking for a check-in API, Foursquare's seems like the best bet at this point. The Venues (ie. places) Platform is especially good, with rate limits starting at 5,000/hr: https://developer.foursquare.com/overview/venues.html
There are other good APIs to consider as well: Google Places, Factual, Yelp, etc. Each API has its own pros and cons in terms of query limits, terms and restrictions, fees, etc.
If you're looking for a check-in API, Foursquare's seems like the best bet at this point. The Venues (ie. places) Platform is especially good, with rate limits starting at 5,000/hr: https://developer.foursquare.com/overview/venues.html