I think Klopp is fine with his CB options - currently Lovren would seem to be #4 in the pecking order , and its an open question as to whether Lovren is fine with that. Given the dodgy health of the non-VVD CBs there seems to be plenty of playing timeLiverpool to offer Milner & Matip extensions. This article states Milner still has a year left, which makes sense. He's too valuable to allow his contract to run down without an extension offer.
Matip has a had a solid season. I think he's fine to retain as a rotation option. The real question is, what to do with the best CB in the world (Lovren)?