@barbs_paul Sorry for the delay in replying Paul. There's no plans for Lollipop for the S4 mini due to memory limitation. >DD— ThreeUKSupport (@ThreeUKSupport) April 24, 2015
Android Lollipop won't be coming to Samsung Galaxy S4 mini units due to memory limitations
If you happen to be one of the relatively few Samsung Galaxy S4 mini owners, we have some bad news: Android 5.0 Lollipop is unlikely to reach your device, now or ever.
Why? Well, according to a tweet sent out by UK carrier Three, TouchWiz based on Lollipop is just too memory hungry, and that makes it impossible for the Galaxy S4 mini's unimpressive hardware to ensure smooth performance. Unfortunately, it seems that the source here isn't just a random PR employee at the network provider – according to the aforementioned tweet, Samsung itself has confirmed that the S4 mini will be getting no love in this regard.
Given how the Samsung Galaxy S4 mini is a mid-2013 model, all of this is honestly unsurprising. Besides, so long as you have Android 4.4 KitKat loaded, you should be more than content enough. If not, then it's probably time for you to upgrade to something a bit more current.