It depends which plan you go for. Assuming you go with the Classic version, obviously all your image files are held locally, so there's no question of them "being held hostage" by Adobe. In fact, even if you end your subscription you will still be able to run Classic in what's termed "reduced functionality" mode....which basically means the Develop and Map modules are disabled, but everything thing else (import, add metadata, export, print, etc.) can still be done. So you could even carry on using the Quick Develop module in the Library module to do some basic editing. If you go with the cloud version, obviously all your images are stored in the cloud and will not be accessible using the desktop app when the subscription ends. However, Adobe has provided a stand-alone app (called the Lightroom Downloader) which will allow you to download a copy of all the images, complete with edits in XMP form, and you will have 12 months following the end of the subscription to download your data.
... View more