Nikon’s consumer DSLR bodies have often refreshed on roughly a 2-year cycle, but it’s not guaranteed. A simple way to see the pattern is to look at a Nikon DSLR timeline (for example, model history charts) and compare announcement dates.

That said, buying decisions based on rumors is risky. Replacements can be delayed, and sometimes there’s no official sign of a successor for quite a while. If the D5100 fits your needs and budget, the practical advice is to buy it rather than wait.

As a first DSLR, you’re unlikely to be limited by being one generation behind. Updates between consumer models are often incremental, and you’ll gain far more by learning exposure, focus, lenses, and composition than by holding out for the newest body. By the time you truly outgrow it, you’ll have a much better sense of which features matter for your next upgrade.