JA megastore template

Hi,

HikaShop will work fine with it.
However, you won't have HikaShop's pages customized to look like the pages of VirtueMart on the template.
For example, if the template has customized the products listing of VirtueMart with some hover effect when you hover on the image of the product, you won't have that effect on the products listing of HikaShop.
So it depends what you mean by "adaptation".
If you mean that you want HikaShop to work fine with the template, it won't be a problem.
If you mean that you want the HikaShop pages to look like the VirtueMart pages, you'll have to add customization to them and it can be a lot of work based on how far you want to go.