Honestly, both drivers should be concerned if Russell does really, really well.
It'll play up to the perception that Bottas is weak and even a number 2 and it'll seal his fate come the 2022 contracts. Meanwhile for Hamilton it would add an extra asterisk to his championships to the large amount of skeptics, given how he has already had the longest streak of utterly dominate cars for 6 seasons (if you minus the first halves of 2017 and 2018 to be generous).
Before I get berated, I'm not denying Hamilton's talent nor dismissing Bottas's good days, which there are enough to justify at least another year at Mercedes for the latter and to be put into the top 10 of all time for the former.