So as noted on the main coronavirus thread there the tennis season is canclled till May. This will in some ways protect Federer's ranking as while he will lose points for being out injured till after the French, others won't be able to defend or gain points either. That said, he's likely to be a good way down the rankings by the time he returns, he could just manager to stay in the top 8 but if there is tennis from May 3rd then he could be around 12- 18th - difficult to be precise on this