In my opinion it is always better to get them in the ground. The roots will have a chance to spread out and the tree will grow much faster. The roots are also more likely to dry out or overheat in a pot. I have always had a hard time with trees in a pot because the summers are hot and dry where I live.

If you wait until after the trees have broken dormancy and the roots are disturbed it could shock the trees. If you are going to put the trees in the ground I would do it as soon as possible.

I planted a Fuyu about the size of yours last year. It had already broken dormancy and had lots of little fruit on it. The dirt kind of fell apart when I took it out of the pot to plant it. It went into shock, dropped all of its fruit, and didn't have any new growth for the rest of the year. After being in the ground for one winter it already has 4x the growth and fruit that it did last year.

I plant asian persimmons directly to the ground when I get them. I have 6 varieties now, including Ichi and Jiro too. They all are doing well. Some of them were much smaller then you described and some of similat to your size. For example Sheng I got last year was about the size of a pencil.
Olga

When I planted my Tam Kam persimmon, it had arrived fully leafed out, in a one gallon container, less than 2 feet tall. I saw no signs of transplant shock. One year later, the following spring, there were lots of feeder roots in a 2 foot radius around the tree, it was well established. I'd suggest planting now, I don't see any advantage to having it in a container any longer.

Alex

Thanks all..for your advice. The reason i was initially hesitant is because i am in zone 6b and was apprehensive on whether the trees need to be a little bigger to have a better chance of surviving winter. Since some of you are also in the same zone as i am, i feel better now and have planted them in the ground. i intend on giving them protection when winter sets in. Any advice on protection. I do not have any space on the south facing side of my house so i planted them about 10 ft away from taller trees but basically on an open area . thanks.

I don't winter protect my persimmons. So far it worked OK (no die back) on Ichi, Jiro, Hana starting from year one. There was some dieback on Sheng, but not too much. This year I added two more tender varieties Chocolate and Coffee Cake. Don't know yet how they will handle 6b zone, but i don't plan to winter protect.
Olga

Ideally you should plant the persimmons in the ground as soon as it is safe to do so, but do consider the expected date of the last frost of the season. If you should plant the tree now and have it leaf out over the next week, you will leave the tree vulnerable to frost for the next several weeks. Persimmons foliage is more sensitive to frost than stone and pome fruit foliage, and a light frost will likely damage your tree, and a deeper frost may well kill it. I lost one newly planted persimmon some years ago just that way. My advice is, if you are able, to keep the tree in a cool dark place until the danger of frost has passed and then plant the hopefully still dormant tree in the ground.

Thanks...i will be mindful of this unpredictable weather. It has been above 80degrees\day, 60deg/nights for the past few days...its gonna drop..to the 40s the next couple nights...I plan to have my small portable greenhouse and some lights around it ..at least until the weather stabilizes.