Some add-ons are being removed as they have been open sourced (and picked up by @Ozzy47 for quite a number). They are also changing their business strategy as they found it not sustainable when doing individual sales of products due to support overhead. Mike has gone over the reasons why throughout his posts.
This isn't uncommon on other platforms when a company begins to outgrow the platform, and they need to decide to focus on the higher end or diversifying their income streams by expanding to other platforms.
The thing today with themes getting deleted was mostly an oversight on our part. XenForo auto deletes resources here if you dont login to the account within 50 days (and we haven't had anything to update regarding the themes and few addons we have) that are public here in that time frame. We manage the replies through our own accounts, so a bit unfortunate. But thanks to XF team for helping to restore.
ThemeHouse will have some products, I imagine all will move to free or open-source overtime (as we've done with UI.X, our WordPress bridge, and hundreds of other products), but overall remains to be seen a bit! As time allows really is my perspective. Always around for those who need us, just yeah focusing on other initiatives. We still have plenty of private and public themes and add-ons, our native app, etc so will be checking in time to time. We have been building custom platforms and such now (some case studies here) and plenty of these use XenForo at their core!