The sanctions against the 3 Oligarchs are the same 3 that have had US sanctions against them in 2018.
It won't go any further, the rest of the Oligarchs (which is numbered to be around 50) have invested in London real estate by the billions, and a few Tories have gotten rich being associated with them.
They are untouchable under this Tory Government, even the US state dept said a few weeks ago because of the money entrenched in London by these Oligarchs that they are practically untouchable under the Tories, to much conflict of interest.