For the 10.0.18 release, I've finished the long project of merging the default and bootstrap templates. The bootstrap theme from 10.0.18 onward will simply be a custom stylesheet for the default theme. This means bootstrap is no longer at risk of getting out of date, either on my end or due to customized templates during your upgrades. If you have an older version of the bootstrap theme you may want to reinstall it in 10.0.18, though you'll have to be careful to reapply your customizations after.
In other recent developments, I've begun automatically updating 9.0 and 9.1 versions to 9.2. Those two series haven't had a release since last year, and it would be complex for me to update them since they're not compatible with PHP 7 which is what I'm running on my development server now. So I figure the best thing for everybody is to just move everyone up to 9.2. Fortunately this doesn't require any admin interaction and all the customized templates can be safely preserved without much risk. Based on my testing, I don't foresee any problems arising, though this is the first time I've tried automated series updates. Of course this only happens when the site is set to automatically upgrade.
Unfortunately it's not so simple to automatically update 7.1 and 8.0 series sites, because there are major changes to the style and fields systems between those versions which would present too much risk of messing up somebody's site while they're not looking. If you are on any pre-9.2 series you do need to upgrade though. I'm planning to write a script to collect a list of known outdated installations and email the owners of those sites to ask them to upgrade, probably sometime within the next month.