Question

Will there be a season 3 of Gravity Falls?

Answer 1

It's been rumored that it's stopping, but the producer of the show announced already that there will, in fact, be a third season.
Hope this helps!

Answer 2

@Babypullmecloser is flat-out wrong. Alex Hirsch has ended the series and does not intend to continue it. It has been recorded that there may be future shows set in the same universe, or even the same characters at a different time, but the intent was to end it completely.