I know that many kids can be resilient when their school situations change. Due to my dh's unusual military assignments, when my ds graduated from high school, he had attended 9 different school systems on 2 different continents plus one remote island. He attended both private and public schools, large and small, plus there was a homeschooling stint for awhile.
So it's possible that your son might do well switching from homeschooling to public school at various times.
But, I'm not convinced that your plans are solidly thought out yet.
First, not all kids can handle going back and forth between school situations, and don't handle change well. My ds was (and still is) one of those people who, from a very early age, could handle anything that got thrown at him. He now works in a very demanding job that is technically challenging and requires that he be able to figure things out in a split second. My dd is the opposite.
Your son is a pre-schooler now. You don't know how he'll handle friendships, structure, school, learning, etc. He might fare better in a quiet home setting and prefer just a light socialization situation, with a friend or two. Or he might thrive in a busy school situation and be the life of the party, so to speak. You might move. I never in a million years imagined that my dh would be assigned to a remote island and my son would attend 10th and 11th grades in a small private school where English was not the first language.
He might need extra resources in case it turns out that he has difficulty in a particular subject area or with a particular skill (reading, or math, for example). In that case, maybe a public school might be better. Only time will tell.
Also, homeschooling can provide a lot of socialization possibilities. There are homeschool groups that get the kids together for art or field trips or classes. Socialization is not the ideal reason to send a child to a public school. Now, if you live on a farm that's far away from other kids and if your son literally doesn't have any kids to play with, and you don't have a church group or nearby friends, for example, maybe public school might provide your son with the chance to make friends and play at recess. But if your son sees friends or cousins, and if you have a homeschooling support group, sending him to public school primarily for socialization might not be the best reason.
My suggestion is to think through why you want to homeschool your son. Religious reasons, lack of a good public school nearby, interest in certain subject areas, personal desire to teach and watch your son learn ... there are lots of reasons.
Don't start planning his high school years yet. He might hate sports, or he might excel in a sport that most high schools don't offer, like fencing or martial arts. He might need something that either homeschooling or public school can provide. To decide his kindergarten choice based on how old he'll be in his freshman year of high school might mean that you're going to overlook something important, and you might lose the focus necessary to start a child out on the right foot in the early years of school.
I suggest that you really evaluate why you want to homeschool, that you really consider your son's temperament and strengths and weaknesses, that you take a good look at what his opportunities for socializing with other kids are right now, and that you decide, based on his current needs and your ability to teach him, what is best for him right now. And go with that. Down the road, he may ask to attend public school. Or he might love his homeschool support group and love the creativity that homeschool can provide, and he might be thriving better than you ever imagined. Or you might find out that you don't love teaching him, and that he's so far ahead in math (or so far behind) that a different school situation is necessary. Focus on the here and now and decide what your son needs now, and what you can provide, and start there.