Personal opinion: 1000 users sounds realistic, but only with a service that appeals the masses, some generic good. I find Japanese learning to be a fairly niche

Personal opinion: 1000 users sounds realistic, but only with a service that appeals the masses, some generic good. I find Japanese learning to be a fairly niche thing, however. Now saying that it's a bad idea, but probably you should readjust your success criteria based on the size of your target market.