@kkdg has created a step by step tutorial on upgrading the custom themes between Vue Storefornt 1.10 and 1.11: https://docs.vuestorefront.io/guide/cookbook/theme.html#_2-how-to-upgrade-theme-one-from-another
VS 1.11 introduced quite a few Vuex modules refactored. As required as they are - unfortunately in some cases introduced non-backward compatible changes.
If you’re on 1.10 you probably don’t have to update your VS soon - we’re offering a Long Time support for the foreseeable future for this line.
From now on, we plan to not introduce any breaking changes, providing the new features - like storefront-ui based theme - as additional, optional modules.
Our key goal is to keep VS easy to upgrade, optimize dev exp. and keep our users safe!
Please read on this new release policy in our recent roadmap update blogpost.