It will take years but you can make it into something
Depending on the length of your growing seasons you can get pretty fast growth from some Japanese Maples. I have one that has been in the ground about 6-7 years. Bought it as a stick cutting of a comparable size to this one about 8 years ago. It is still in the ground at a rental property I own, but the trunk on it is already HEFTY. I have debated about digging it up and making a Bonsai from it, but it is such a nice landscape tree I think I have to leave it now. I have air layered a couple trees off it over the years and even the air layers have respectable trunks in the 1.5-2 inch range. I just repotted one to a training pot this year and chopped it to start working it into a Bonsai, the others are probably going to get more work next year...
I know the cultivar you are working with is more of a dwarf variety and will grow a good bit slower, I am talking about a standard green variety...
As far as planting this tree somewhere... Put it in the ground now if you want. Just keep it a little more wet than you normally would until you see new growth and have a good idea it is making new roots. The danger with repotting this time of year is you don't want to take an established tree, pull it out the pot, prune roots, do a big overhaul... That is a recipe for disaster in the heat of the summer! If you want to move that tree to a bigger pot to let it grow, or put it in the ground you can pretty much do that with just about any tree even at this point in the summer.
Up potting or planting in the ground isn't nearly as stressful on the tree as repotting an old established bonsai and doing root work would be... Yeah, it is BEST to repot in the Spring or Fall, but if you are just taking a tree out that tiny nursery pot, and carefully moving to a nice partially shaded spot in your yard or a bigger pot without disturbing the roots much, The tree will barely notice it was touched. I have done it with everything from Pines to Maples to Elms and if you think about it, landscapers would only be able to work like 1 month out the year if you couldn't plant trees/ shrubs in the ground during the summer! I just planted a crepe Myrtle in the ground this past weekend, and it is a pretty sunny spot. it is doing fine after almost a week... It was actually getting a bit pot bound in it's little pot when I got it a couple weeks ago and was wilting during hot days. After a couple days In the ground, and keeping it pretty moist, the tree is thriving already and holding up a lot better than it did in a pot. In my humble opinion, if growth is your goal (as it should be) there is no reason to wait another 10 months or so to plant that thing! Get it started now, don't prune it for a couple years, let it go strong In regular garden soil, fertilize well... And see what you have in a couple years, then start worrying about shape.
Good luck!
