Restrictions on hand luggage, on incoming flights to the UK (other than from the US), remain unchanged after the events of last week. (i.e. incoming passengers, other than from the US, have continued to be permitted to carry hand luggage, with no changes to the permissible contents of that luggage).
However, most airlines have restrictions on the size of hand luggage which would prohibit anyone from carryng a 4 foot high carving. (Additionally, most airlines only permit one item of hand luggage so, if you've also got a flight bag, you'd still be prohibited from taking such a carving into the cabin). It seems that your parents managed to get away with breaching the regulations.
To summarise: There are no new regulations to prevent you carrying the carving. However, you may still be prohibited from carrying it if the airline enforces existing rules.
Chris