The best web site to follow the box office evolution of Valkyrie is Mojo.
We can see here that with $8.12, not only Valkyrie maintains its position well, but it has lost only 2.7% compared to the preceding day. Of the four leaders, it is the one who lost public interest less, which means it is catching up a bit. Compare this with Brad Pitt losing 13.6% (but still remaining 2nd).
PS - With 2,758 theaters showing Valkyrie, it only comes in 7th position. This is 923 theaters less than Adam Sandler, and 722 less than Aniston. Counted by theater, Cruise would be 3rd rather than 4th.