There was a plan that Makie should eventually replace (or merge with) Plots. I would appreciate if someone in the know would give an update on the current state of affairs regarding this.
I think Makie is unlikely to merge into Plots. Makie already uses some of Plots color and axis utilities (by PlotUtils), and there is a plan to make Makie consume recipes defined with RecipesBase, at which point Makie will be able to drop-in for Plots for plotting custom types from packages. This is by far the most important use case of Plots IMHO, and given that Makie is more modern and customisable that is likely to lead to it replacing Plots. I don’t know how far advanced coding up for that solution is, but I don’t think very far.
Note though that Makie has a very different relationships to backends. There is a proof-of-concept GR backend for Makie but the mechanics are different from the relationship between GR and Plots.jl. The syntax is also slightly different, though similar. But Makie is perfectly usable now (made much more approachable by static compilation) and Plots is still completely usable and maintained.
Thank you for the answer and your work on the Julia plotting ecosystem! Recipes was actually the main reason why I asked; glad to hear that this is the plan - sounds perfect!