Linux+ has not yet been mentioned by CompTIA as having a renewal requirement.
The policy is given here,
CompTIA Certification Renewal Policy
and only states that A+, Network+, and Security+ will have a renewal requirement for those certs issued after 12/31/2010. So far, all other CompTIA certs remain in effect for lifetime.
The new Linux+ has not been released yet, and it is anticipated that they will do that in late March.
CompTIA Linux+ is the information site for this exam.
Yes, XK0-002 is the code for the present exam. Generally, the present exam is available for a while even after the new CompTIA exams are released, and can still be taken for a few weeks. Basically, the new exam guide should be used for the new and the old guide for the old to be sure that every subject of the exam objectives are covered. You should download the exam objectives and compare any study guide to the objectives of that particular version of the exam to be sure.
Hope this helps. Good luck!