It's certainly possible Thomas joins the liberals here, but even then, there's still probably five votes to overturn it on the current court (assuming Roberts's history on voting rights continues into present decisions).
That's potentially a bold assumption to make, given that one of Roberts' problems with the old pre-clearance provisions was that they only applied to a few states, whereas the John Lewis V.R.A.'s pre-clearance provisions would apply to all 50.
Even then, Roberts is still only four votes if they can't convince another Conservative (I'd assume that person would be Thomas, being an African-American Justice, would be the next most likely to uphold the John Lewis Voting Rights Act.)
What’s that got to do with this?
Fwiw, he’s thought of as the most ‘conservative’ Justice and he wrote a wider concurrence arguing that they should have struck down preclearance in its entirety.