Future boosters don't necessarily need to be based on mRNA tech. Novavax, for example, is a protein-subunit vaccine. mRNA may have an advantage in rapid development and fast manufacturing, however.
Those are good points, thanks. Probably makes sense for people who got mRNA to switch to non-mRNA for ongoing boosters, to be cautious. But the advantages you cite will surely cause pressure to use it more, especially for moving targets like the flu. I hope we have more details soon about the bounds of "multiple doses" and the potential issues associated.