Perhaps but not necessarily. Hibiscus leaves turn yellow and drop from the plant due to stress. The stress can be of any type, and figuring out what kind of stress is the challenge. YOU have to think about it, and when you are pretty sure you have determined the cause, then you can take action to relieve the stress on your hibiscus.
Is it a hardy Hibiscus or tropical Hibiscus? The tropical variety has shiny leaves where the hardy variety doesn't. You can also tell the difference by the color....hardy Hibiscus do not come in yellow, orange, peach, salmon and do not produce a double blossom. The Tropical Hibiscus does need to be taken in during the winter if your temps drop much below 40 degrees. It will loose it's leaves but will put out new growth in the late spring. Don't expect them to bloom year round or to keep their leaves year round, they need a rest period too. And they do need to be kept on the cool side in a bright location or under grow lights. Cooler temps will prevent pest problems later in winter.