If the wealthy do decide to hold their wealth in other forms, this could potentially free up land for more productive uses or for those who might not have had access to land ownership before. This could lead to a more equitable distribution of land, which is a form of wealth in itself.
The argument that the wealthy will simply shift their wealth to other less-taxed or non-taxed forms is not necessarily a critique of the LVT, but rather a critique of the overall tax system. If other forms of wealth are undertaxed, the solution would be to reform these areas of the tax system, rather than reject the LVT.