No I doubt it very much (although css doesn’t really get deprecated in the same way as html elements anyway). It will work fine in 10 years time just as it did 10 years ago and just as color and display will work.
Indeed its your grid layout that may not work as the spec is still changing and the next level of subgrids being introduced which may affect the way that sites currently designed work. The same issues arose with flexbox and you still have IE using older versions. If you are talking about longevity then for the next year or so display:table still has the edge.
Display:table is a grid like layout unlike flexbox as flex is linear. You can do things with display:table that can’t be done easily by other methods and uses algorithms that have been present in the browsers since the table layouts of the 1990s.
Just because something is new doesn’t mean you have to use it. You use the tools required for the job in hand whatever you think fits the purpose the best.
In the end they are all tools in the toolbox and as usual with CSS there are often many ways to do the same thing and whether they are right or wrong depends on the job in hand and on personal preference.
Of course things like using floats for columns should be avoided as there are better methods but that doesn’t mean you can’t float something when you need to as neither grid of flex can imitate a float.