first i would say they will rise because gdp will fall in line with debt increases. second it does not take future liabilities into account such as pension payments. the uk is said to have to pay 76 percent of gdp on pensions in the coming years.
The numbers in the table posted are pretty much useless by themselves. Some countries have effectively no debt. Norway, for example, does issue debt instruments to facilitate cash flow, but could if needed pay off all government debt very quickly.
These figures by themselves are meaningless. Japan tops the list, but remember Japan holds $746 Billion worth of Trasury Bonds. A real figure would be debt LESS RESERVES, divided by the GDP.
I would love to understand how FX reserves held by the Bank of Japan matter to the level of indebtedness of the Japanese govt... In truth, due to the various quirks in Japanese accounting methods, the net debt/GDP figure for Japan is more like 170% or so (although opinions vary). However, it's never been about FX reserves. Obviously, if the BoJ decides to monetize govt debt and depreciate the yen, it becomes a different kettle of fish.