Twitter has bought Cover, an Android lock screen replacement that automatically places apps that it thinks you'll want to use front and center based on your location and the time of day. Cover suggests that development will cease on its eponymous app for the time being, though it says that the app will remain available in the Play Store.
It's likely then that Twitter isn't interested in taking over your lock screen so much as it's interested in Cover's creators and their experience with intelligently surfacing information — something that it can certainly put to use.
If Twitter is interested in taking over your lock screen, this acquisition would instead be the start of a far more ambitious initiative.
Twitter too could try for something like this by expand Cover's abilities beyond apps and into tweets, news, and trends. For now it appears that Twitter isn't interested in this — it's certainly seen the lack of demand for Facebook Home — but we may just see a smarter version of its Android app sometime down the road.