Having missed Christmas Day church services due to a heavy cold, Queen Elizabeth II needed to remain at home and recover, Buckingham Palace said. However, she still enjoyed her family's Christmas Day celebrations.

But apart from missing the church services, rumors whisper that the 90-year-old reigning, longest serving monarch will be retiring soon. She handed over patronage of more than 20 national organizations recently.

She is phenomenally rich, of course. With the cost of the land and real estate values in the United Kingdom, just her nominal assets totted up to about 22.8 billion pounds, or $34.8 billion, in 2015. Now that is just for starters.

One can take a look at her list of fortunes at Yahoo. It explains, "She makes American billionaires Michael Bloomberg and Facebook founder Mark Zuckerberg seem like Average Joes."

Anyway, who will be the next royal to sit on the throne after her?

Her elder son, Prince Charles, has the titles of Prince of Wales, Duke of Rothesay and the Duke of Cornwall, according to IB Times. Although he has been waiting for years to become King, his wife, Camilla, cannot be the queen. As they had an extramarital affair while he had been married to Princess Diana, Camilla would be called only the princess consort.

It is Charles' oldest son, Prince William, who will step into the shoes of the Prince of Wales and become heir to the throne. His eldest son, George Alexander Louis, is currently the third in line to the British throne. Hence, the son of Kate Middleton and Prince William holds the title of Prince of Cambridge.

Next in the queue is Prince Harry, the second son of Charles and Diana. He is fourth in line as King of England.

Still, all those possibilities and speculations are quite far away, as Queen Elizabeth's health is poorly but still healthy for her age. Nicholas Witchell, BBC News' royal correspondent, said the Queen's absence from Christmas Day service Sunday can be seen as a "precautionary measure." However, there is "no sense of undue concern" from Buckingham Palace, he clarified.