I wonder if Pence and the cabinet have already done so, in secret? Apparently it was Pence, not Trump, who ordered in the National Guard [1], and there doesn't seem to be any requirement in 25/4 that Pence and the cabinet inform anyone but the President pro tempore and Speaker that they have done as much.

[1] https://www.cnn.com/2021/01/06/politics/pence-national-guard...