As a daycare provider, I try to fill spots with children who are ages that would mesh well. Now saying that, it isn't always possible and at times I have to fill the spaces with the ages given to me in order to pay my bills.

In home daycare, there won't always be the guarantee that your child will have friends the same age. For some kids this is okay but I have had situations where the older child gets bored, acts up, regresses etc. One child in particular did not handle being the oldest (by two years in age but at least 3-4 years in mental age) well and in the end they pulled her out to attend preschool for a year and a half before starting Kindergarten. It really was in the best interest of the child and I hope that it also curbed some of her behaviour. (some of it was just due to lack of parenting but that's another story lol)

It would depend on the daycare provider as well. Does she have toys/games/activities that are still going to stimulate your child or is the focus on the little kids? I have 2 under 2, 2 three year olds and an almost 4 year old. I spend some time with the older kids doing things that the little ones aren't ready for (they are welcome to watch of course but my focus is on the older 3). Ask your provider what her plans are and go from there maybe?

Also, keep in mind, that lots of moms/dads stay home with their children and will have this same situation. It isn't the end of the world but depending on what you want your child to get out of daycare will determine if this is still a good fit for you and your child. Do you have time in the evenings to work/play with your child on more age appropriate activities. A good daycare provider can be hard to find so if you have one, sticking with her might be better than finding a preschool with a mediocre teacher for example.