I am not sure it will decline foreign investments in Russia in general. In this case it is simply Russia retaliating against the Western banks which have frozen Russian assets. I don't think banks from the rest of the world outside of the "garden" will be concerned and they will likey fill the gap. It might cause some stir in the financial circles in the West who willingly followed the sanctions regime as they are now feeling what it is like to have money in another country which you can't access.
You play with fire at the risk of getting burned.